Anaphylaxis caused by the new ant, Pachycondyla chinensis: demonstration of specific IgE and IgE-binding components

Global View on Ant Venom Allergy: from Allergenic Components to Clinical Management

Hymenoptera venom allergy is characterised by systemic anaphylactic reactions that occur in response to stings from members of the Hymenoptera order. Stinging by social Hymenoptera such as ants, honeybees, and vespids is one of the 3 major causes of anaphylaxis; along with food and drug exposure, it accounts for up to 43% of anaphylaxis cases and 20% of anaphylaxis-related fatalities. Despite their recognition as being of considerable public health significance, stinging ant venoms are relatively unexplored in comparison to other animal venoms and may be overlooked as a cause of venom allergy. Indeed, the venoms of stinging ants may be the most common cause of anaphylaxis in ant endemic areas. A better understanding of the natural history of venom allergy caused by stinging ants, their venom components, and the management of ant venom allergy is therefore required. This article provides a global view on allergic reactions to the venoms of stinging ants and the contemporary approach to diagnose and manage ant venom allergy.

Worldwide perspectives on venom allergy

Venom immunotherapy is the standard of care for people with severe reactions and has been proven to reduce risk of future anaphylactic events. There is a moral imperative to ensure production, supply and worldwide availability of locally relevant, registered, standardized commercial venom extracts for diagnosis and treatment. Insects causing severe immediate allergic reactions vary by region worldwide. The most common culprits include honeybees (Apis mellifera), social wasps including yellow jackets (Vespula and Dolichovespula), paper wasps (Polistes) and hornets (Vespa), stinging ants (Solenopsis, Myrmecia, Pachycondyla, and Pogonomyrmex), and bumblebees (Bombus). Insects with importance in specific areas of the world include the Australian tick (Ixodes holocyclus), the kissing bug (Triatoma spp), horseflies (Tabanus spp), and mosquitoes (Aedes, Culex, Anopheles). Reliable access to high quality venom immunotherapy to locally relevant allergens is not available throughout the world. Many current commercially available therapeutic vaccines have deficiencies, are not suitable for, or are unavailable in vast areas of the globe. New products are required to replace products that are unstandardized or inadequate, particularly whole-body extract products. New products are required for insects in which no current treatment options exist. Venom immunotherapy should be promoted throughout the world and the provision thereof be supported by health authorities, regulatory authorities and all sectors of the health care service.

Hymenoptera venoms used to produce allergen extracts

OBJECTIVE

To review the methods and materials used for collection, purification, commercial production, and clinical application of Hymenoptera venoms.

DATA SOURCES

Most of the sources for this review are the experience and expertise of the authors. Published reports and review articles on Hymenoptera venom collection and production were identified through database searches (PubMed).

STUDY SELECTIONS

Studies describing the methods for Hymenoptera venom collection and production were selected for review.

RESULTS

Meticulous methods for identification and collection of the insects are required. Collection and purification of the venoms from the insects are based on validated methods and result in a commercial extract that is standardized for the major allergenic proteins required for accurate diagnosis and safe and effective treatment of patients allergic to insect sting. The steps required for mixing, purifying, testing, and standardizing the products are described.

CONCLUSION

Hymenoptera venom extracts were developed using many new methods for the collection, purification, and commercial production of the unique materials required for this product. Clinical applications for diagnosis and treatment are affected by the integrity and stability of the allergens after processing and purification.

[Cross reactions between Hymenoptera venoms from different families, genera and species]

Simultaneous reactivity with the venoms of different Hymenoptera is commonly seen in patients allergic to insect venoms. Strong, though individually variable, cross-reactivity occurs between the venoms of different Vespinae species (Vespula, Dolichovespula, Vespa). In Middle Europe, anaphylaxis after European hornet stings is nearly always due to cross-reactivity with Vespula venom. The identification of the primary venom in patients testing positive for Vespula and Polistes (paper wasps) is particularly important in Mediterranean areas. Component-resolved diagnosis with the marker allergens Ves v 5 and Pol d 5 may directly identify the causative venom in the majority of patients. There is substantial cross-reactivity between honeybee and bumblebee venom, sometimes causing allergic symptoms in patients allergic to honeybee venom after accidental bumblebee stings. However, subjects strongly exposed to bumblebees may show bumblebee-specific sensitization and require immunotherapy with bumblebee venom. More than half of all venom-allergic patients show double-positive test results to honeybee and vespid venoms. This may be due to true double sensitization or due to cross-reactivity between homologous allergens present in both venoms and sharing around 50 % sequence identity, i.e. hyaluronidases (Api m 2/Ves v 2), dipeptidyl peptidases (Api m 5/Ves v 3), and vitellogenins (Api m 12/Ves v 6). The clinical relevance of these cross-reactions is unknown. In up to 50 % the double-positivity is caused by clinically irrelevant IgE antibodies against CCDs. Many (though not all) patients with true double sensitization may be identified by means of the species-specific marker allergens Api m 1 and Ves v 1/5. Some Vespula venom-allergic patients may clinically cross-react to fire ant stings (Solenopsis), but otherwise allergen relationships with other ant species are not well studied.

Human sting of Cephalonomia gallicola (Hymenoptera: Bethylidae) in Korea

Hymenoptera stings can cause serious injury to humans. We report the clinical findings of 6 cases of Hymenoptera stings. All patients developed painful erythematous papules at the sting sites and had a past history of parasitoid wasp sting. This is the first clinical report of the parasitoid wasp, Cephalonomia gallicola, causing human stings in Korea.

A new (old), invasive ant in the hardwood forests of eastern North America and its potentially widespread impacts

Biological invasions represent a serious threat for the conservation of biodiversity in many ecosystems. While many social insect species and in particular ant species have been introduced outside their native ranges, few species have been successful at invading temperate forests. In this study, we document for the first time the relationship between the abundance of the introduced ant, Pachycondyla chinensis, in mature forests of North Carolina and the composition, abundance and diversity of native ant species using both a matched pair approach and generalized linear models. Where present, P. chinensis was more abundant than all native species combined. The diversity and abundance of native ants in general and many individual species were negatively associated with the presence and abundance of P. chinensis. These patterns held regardless of our statistical approach and across spatial scales. Interestingly, while the majority of ant species was strongly and negatively correlated with the abundance and presence of P. chinensis, a small subset of ant species larger than P. chinensis was either as abundant or even more abundant in invaded than in uninvaded sites. The large geographic range of this ant species combined with its apparent impact on native species make it likely to have cascading consequences on eastern forests in years to come, effects mediated by the specifics of its life history which is very different from those of other invasive ants. The apparent ecological impacts of P. chinensis are in addition to public health concerns associated with this species due to its sometimes, deadly sting.

Household arthropod allergens in Korea

Arthropods are important in human health, which can transmit pathogens to humans, parasitize, or produce important allergens. Allergy prevalence becomes higher in Korea recently as well as other developed countries in contrast to a decrease of infectious diseases. Allergic diseases caused by household arthropods have increased dramatically during the last few decades since human beings spend more their time for indoor activities in modernized life style. Household arthropods are one of the most common causes of allergic diseases. Biological characterization of household arthropods and researches on their allergens will provide better understanding of the pathogenesis of allergic diseases and suggest new therapeutic ways. Therefore, studies on arthropods of allergenic importance can be considered one of the major research areas in medical arthropodology and parasitology. Here, the biology of several household arthropods, including house dust mites and cockroaches, the 2 most well known arthropods living indoor together with humans worldwide, and characteristics of their allergens, especially the research activities on these allergens performed in Korea, are summarized.

Characterization of the major allergens of Pachycondyla chinensis in ant sting anaphylaxis patients

BACKGROUND

The ant species Pachycondyla chinensis, which has spread from Far Eastern Asia to New Zealand and North America, induces anaphylactic reactions in human with its sting. However, the major allergens of P. chinensis have not yet been characterized.

METHODS

We selected seven patients with histories of anaphylaxis induced by P. chinensis. Two-dimensional electrophoresis (2-DE) was used to identify the major allergens. We subsequently performed Western blots for P. chinensis-specific IgEs, N-terminal amino acid sequencing, ESI-MS/MS, and RT-PCR using primers based on the N-terminal sequence.

RESULTS

Six of the anaphylactic subjects had an IgE specific to a 23 kDa allergen of P. chinensis. Two candidates for major allergens, 23 kDa (pI 8.7) and 25 kDa (pI 6.2), were revealed by 2-DE using P. chinensis-specific IgE immunoblotting. In N-terminal sequencing and ESI-MS/MS analysis, 23 kDa (pI 8.7) and 25 kDa (pI 6.2) allergens, belonging to the protein families of antigen 5, were identified and share marked amino acid sequence similarity. The 23 kDa allergen is 206 amino acids in length and homology searches showed 54.0% and 50.0% homology with Sol i 3 and Ves v 5, respectively.

CONCLUSION

The major allergens of P. chinensis are 23 kDa (pI 8.7) and 25 kDa (pI 6.2) proteins that belong to the antigen 5 family of proteins.

Epidemiologic and clinical features of anaphylaxis in Korea

BACKGROUND

Little is known about the characteristics of anaphylaxis in Korea or even in Asia.

OBJECTIVE

To evaluate the incidence of anaphylaxis and the clinical features of patients with anaphylaxis in a Korean tertiary care hospital.

METHODS

We performed a retrospective review from January 1, 2000, through July 31, 2006, of 138 patients with anaphylaxis, including inpatients, outpatients, and emergency department visitors, in the Seoul National University Hospital.

RESULTS

Among 978,146 patients, 138 (0.014%) had anaphylaxis. Two cardiopulmonary resuscitations were performed and 1 death occurred. The total mortality rate of anaphylactic patients was 0.0001%. The causes of anaphylaxes were drug (35.3%), food (21.3%), food-dependent exercise-induced (13.2%), idiopathic (13.2%), insect stings (11.8%), exercise induced (2.9%), blood products (1.5%), and latex (0.7%). Radiocontrast media and buckwheat were the leading causes of drug and food anaphylaxis, respectively. The organs most frequently involved in the anaphylaxis were cutaneous (95.7%), cardiovascular (76.8%), and respiratory (74.6%). The most common manifestations were dyspnea (71.3%), urticaria (81.9%), and angioedema (69.4%). Three of 138 patients (2.2%) had biphasic reactions.

CONCLUSIONS

The incidence, mortality rate, and clinical features of Korean patients with anaphylaxis were similar to rates for patients from other countries, despite some differences in causative agents.

Animal bites and stings with anaphylactic potential

Anaphylaxis to animal bites and stings poses a significant medical risk of vascular or respiratory reactions that vary according to the patient's response and nature of the insult. Emergency Physicians frequently see patients who complain of an allergic reaction to an animal bite or sting. Although Hymenoptera stings, specifically those of wasps, bees, and hornets, account for the majority of these cases, other invertebrates and vertebrates are capable of causing allergic reactions and anaphylaxis. Many of the causative animals are quite unusual, and their bites and stings are not commonly appreciated as potential causes of anaphylaxis. We conducted a literature review to identify documented reports of anaphylaxis and anaphylactoid reactions to animal bites and stings. This summary is meant to heighten awareness of the diversity of animals that may cause anaphylaxis, hopefully leading to more rapid diagnosis and treatment of this dangerous condition. A diverse group of animals was found whose bites and stings cause anaphylaxis and anaphylactoid reactions. Some case summaries are presented. A potentially life-saving plan is to direct patients to proper follow-up care to prevent a future life-threatening reaction, including: prescribing epinephrine and antihistamines with proper instructions for their use; referral to an allergist to determine if skin testing, radioallergosorbent test, and immunotherapy are indicated; and reporting the case to state or local Poison Control Centers. In some cases it may be helpful to consult an entomologist or a pest control service for help in identification and elimination of certain offenders.

Emergence of the introduced ant Pachycondyla chinensis (Formicidae: Ponerinae) as a public health threat in the southeastern United States

Pachycondyla chinensis (Emery) (Formicidae: Ponerinae), a species introduced into North America > 70 yr ago, is found throughout Southeast Asia. Stinging of zookeepers by P. chinensis at the Greenville Zoo (Greenville, SC) initiated an investigation of this exotic species and a survey of sting victims. Eighty percent of sting victims experienced local reactions, including swelling < 5 cm in diameter around the sting site, recurring pain, skin redness, and mild-to-severe urticaria. These symptoms lasted 2 h to 5 d. Twelve percent of the sting victims reported minor reactions, including no swelling, localized redness, minor pain sensation at the time of sting, mild urticaria, and symptoms lasting < 1 h. Eight percent of the sting victims reported significant local reactions, including swelling > 5 cm in diameter around the sting site, recurring pain, skin redness, severe urticaria, and symptoms lasting 3-14 d. P. chinensis represents an emerging public health threat throughout its present range in the southeastern United States (i.e., Georgia, North Carolina, South Carolina, and Virginia). Because of reported adverse reactions to stings of P. chinensis, further studies on its ecology and medical and veterinary importance need to be undertaken.

Hymenoptera venom allergens

Hymenoptera venoms each contain a variety of protein allergens. The major components have all been characterized, and most of the amino acid sequences are known. This article concentrates on the use of contemporary techniques including cloning, mass spectrometry and genomics in the characterization of venom allergens, and newer separation techniques for protein isolation. Examples of the use of these techniques with venom proteins are presented.

Adverse reactions to ants other than imported fire ants

OBJECTIVE

To identify ants other than Solenopsis invicta and Solenopsis richteri reported to cause adverse reactions in humans.

DATA SOURCES

We conducted a literature review to identify reports of medical reactions to ants other than S. invicta and S. richteri. Our review of medical and entomological literature on stinging ants was generated from MEDLINE and FORMIS, respectively, using the key words stinging ants and ant stings. The search was limited to articles in English published from 1966 to 2004 on MEDLINE and all years on FORMIS. We also present 3 new case reports of severe reactions to stings by 2 different species of ants, Pseudomyrmex ejectus and Hypoponera punctatissima.

STUDY SELECTION

Articles that concerned anaphylactic (IgE-mediated) or anaphylactic-like (resembling anaphylaxis but mechanism unknown) immediate reactions to ant stings or bites were included in this review.

RESULTS

Taken together, our data demonstrate that S. invicta and S. richteri are not alone in their capability to cause serious allergic or adverse reactions. A diverse array of ant species belonging to 6 different subfamilies (Formicinae, Myrmeciinae, Ponerinae, Ectatomminae, Myrmicinae, and Pseudomyrmecinae) and 10 genera (Solenopsis, Formica, Myrmecia, Tetramorium, Pogonomyrmex, Pachycondyla, Odontomachus, Rhytidoponera, Pseudomyrmex, and Hypoponera) have now been shown to have this capability.

CONCLUSION

Awareness that species other than imported fire ants may cause severe reactions should lead to more rapid evaluation and treatment and further investigation of the medical entomology of these ants.

Systemic immediate allergic reactions to arthropod stings and bites

Most of the encounters with biting and stinging insects result in more or less pronounced localized reactions. Typically, urticarial wheals and papular reactions are observed. Less often local bullous or hemorrhagic or disseminated papular reactions, particularly in children and immunologically naive adults, may be seen. With the exception of bee and wasp venom allergies, immediate-type allergic reactions to arthropod stings and bites are rare. Systemic IgE-mediated hypersensitivity has also been reported from additional hymenoptera species, e.g. hornets, bumble bees and ants. Rare are systemic reactions to mosquitoes, flies or kissing bugs and exceptional from ticks, bed bugs, moths, caterpillars and spiders. A major problem is the often lacking standardization of extracts for skin testing and for the determination of specific IgE. Some of the allergens have been characterized and few of them synthesized using recombinant techniques. Most investigations have been made with whole-body extracts or extracts from salivary glands, while desensitization has rarely been attempted. Currently, primary prevention by avoidance of stings and bites, and adequate instruction of sensitized individuals in the use of emergency drugs are mandatory.

Insect sting reactions to bees, wasps, and ants

Abstract Arthropod bites and stings are capable of inflicting injury, inciting allergic reactions, and transmitting systemic disease. Members of the Hymenoptera order are of particular importance because they are nearly ubiquitous in nature, and their stings may cause life-threatening allergic reactions. Stings from bees, wasps, and ants produce a variety of clinical and histological manifestations. Anaphylaxis following an insect sting is the most serious complication. For individuals with a specific allergy to Hymenoptera venom, immunotherapy may be a relatively safe and effective treatment option.

Respiratory allergy to the indoor ant (Monomorium pharaonis) not related to sting allergy

BACKGROUND

Many studies are available on systemic reactions to ant sting, but few have described the direct role of ants in respiratory allergy. The nonstinging house ant, Monomorium pharaonis (pharaoh ant), is a highly infesting species in indoor environments.

OBJECTIVE

To determine whether the pharaoh ant is an indoor source of aeroallergens.

METHODS

Two patients with asthma who lived in homes with ant infestation were enrolled. Pharaoh ants were collected at the patients' homes, and crude extracts were prepared. Skin prick tests with ant extracts were performed. Specific IgE to pharaoh ant was measured by enzyme-linked immunosorbent assay (ELISA), and the allergenic components were determined by using immunoblot analysis. Cross-reactivity among pharaoh ant, imported fire ant, Pachycondyla chinensis ant, and other indoor allergens was evaluated by ELISA inhibition tests. Specific bronchial challenge testing was performed using pharaoh ant extracts.

RESULTS

Both patients had positive skin test reactions to pharaoh ant extract and high levels of specific IgE antibodies to pharaoh ant. The ELISA inhibition test results demonstrated significant inhibition by pharaoh ant; however, P. chinensis, cockroach, and house dust mite showed no inhibition of the IgE binding to pharaoh ant. Two important IgE-binding components, 9.4 and 34 kDa, were identified by using immunoblot analysis. Pharaoh ant bronchial challenge test results showed typical early asthmatic reactions in 1 patient and dual asthmatic reactions in the other patient.

CONCLUSIONS

Ants can induce IgE-mediated bronchoconstriction regardless of sting in sensitized patients. Ants should be taken into consideration as a cause of respiratory allergy in patients living in homes with visual evidence of infestation.

Prevention of anaphylaxis with ant venom immunotherapy

PURPOSE OF REVIEW

Worldwide, eight genera of ants have been associated with sting allergy. Until recently only whole ant body extracts have been used for immunotherapy. The purpose of this review is to examine recent advances in the understanding of ant venom allergy and treatment using venom immunotherapy.

RECENT FINDINGS

Public health problems due to severe ant sting anaphylaxis are not confined to the imported fire ant of North America. Pachycondyla sennaarensis (samsum ant), Pachycondyla chinensis, and Myrmecia pilosula (jack jumper ant) also appear to pose notable threats. The risk to humans from a particular species probably depends on complex interactions between likelihood of human contact, insect aggression, efficiency of the venom delivery apparatus, and venom allergenicity. The highest population prevalence of clinical ant sting allergy so far (3.0%) was reported from south-eastern Australia, due mainly to M. pilosula. Prospective follow-up of untreated people suggests that those older than 30 years with a history of severe reactions (respiratory compromise or hypotension) will benefit most from venom immunotherapy. Whereas the efficacy of ant whole body extract immunotherapy remains to be proven, ant venom immunotherapy has been demonstrated to reduce the risk of systemic reactions to M. pilosula from 72% to 3%. Although a simple method of venom extraction has been developed, small market size means that the treatment may never become widely available.

SUMMARY

Ant venom immunotherapy is feasible and highly efficacious. However, the limited geographical distribution of each species presents a major challenge to making venom extracts available for clinical use.

Ant allergy in Asia and Australia

PURPOSE OF REVIEW

Anaphylaxis due to ant sting is increasingly being recognized as a significant problem. Severe allergic reactions to ants are well described in the south-eastern United States, but have only been recognized in recent years as being important in other parts of the world. There are many different ant species and their distribution around the world varies. The purpose of this review is to familiarize the reader with the epidemiology and clinical characteristics of ant allergy in Asia and Australia.

RECENT FINDINGS

In Korea, allergy to Pachycondyla chinensis (subfamily Ponerinae) has been well described. In an ant-endemic area, sensitization was 23%, with about 1% having anaphylactic reactions. There were at least eight IgE-binding proteins in P. chinensis venom, with 1 major allergen binding 85% of patient sera. P. chinensis venom was also found to be possibly crossreactive with bee venom, but not with imported-fire-ant venom. In Australia, anaphylactic reactions to ant stings are usually caused by the 'jack jumper' ant (Myrmecia pilosula) or the bull ant (Myrmecia pyriformis). A recent study showed promising results for immunotherapy with M. pilosula venom. There have been reports of stings by other ant species in Asia and Australia, but these reports are few and sporadic.

SUMMARY

The study of ant allergy in Asia is in its infancy. Clinicians in Asia need to be aware of ant stings as a cause of severe allergic reactions. Certain species that cause allergic reactions are unique to Asia and Australia and deserve further research. The allergens in the venom of the different ant species need to be identified. We should aim for improved understanding of the epidemiology of ant-sting anaphylaxis, formulation of better diagnostic tests and possibly the introduction of immunotherapeutic strategies.

Patients with negative skin tests

PURPOSE OF REVIEW

The aim of this article is to present and discuss the clinical problem of systemic anaphylaxis to Hymenoptera venoms in patients without detectable immunoglobulin E, as it appears in recent literature. Reported at variable frequency in large series of patients undergoing evaluation, systemic anaphylaxis was previously considered to reflect lost sensitization or to involve non-immunoglobulin E mediated mechanisms. Sporadic case-reports drew attention to the fact that severe or even fatal reactions may occur in patients with negative skin tests.

RECENT FINDINGS

A breakthrough article by Golden et al., who performed deliberate stings on skin test negative venom anaphylaxis patients, demonstrated that clinical sensitivity was still present in a subset of these subjects and pointed out to the limitations of present diagnostic methods or reagents. New immunobiochemical methods and highly specific recombinant allergens--when all clinically relevant Hymenoptera venom allergens have been identified, cloned, sequenced and expressed in the proper system--are anticipated to increase the diagnostic yield. Non-specific mechanisms causing anaphylactoid reactions will probably explain some enigmatic, skin test negative radioallergosorbent test negative cases in the future. Occult mastocytosis, predisposing patients to anaphylactoid reactions, has been reported with increasing frequency among skin test negative patients. Lastly, other causes mimicking venom anaphylaxis may on rare occasions contribute to the problem.

SUMMARY

With the present understanding of venom allergy, the practising clinician is not infrequently faced with the dilemma of the skin test negative patient. Once other identifiable causes have been carefully ruled out, referral to a specialized center for deliberate sting-challenges appears in selected cases to be a medically appropriate and ethically justified management approach.

Diagnosis of Hymenoptera venom sensitivity

PURPOSE OF REVIEW

The objective of this review is to highlight recent advances in the preparation, documentation and performance of reagents and methods used in the diagnosis of Hymenoptera-venom-induced immediate-type hypersensitivity.

RECENT FINDINGS

The following potent allergens have been reported: (1) a low-molecular-weight honey-bee allergen (Api m 6) has been described; (2) venom allergens in the North American species of bumble-bee (Bombus pennsylvanicus) have been more fully characterized, with the focus on phospholipase A2; (3) the vespid venom Ves v 5 allergen has been structurally mapped to identify immunoglobulin-E-binding epitopes; (4) the possible role of carbohydrate antigen epitopes as a cause of cross-reactivity among honey-bee and vespid venom proteins has been reported; and (5) the venom of Pachycondyla chinensis, an ant found commonly in the Far East, has been described. The most significant reports during this period have focused on the less-than-ideal performance of the intradermal venom skin-test reagents. The issue of the patient that is positive for venom allergy history but negative for an intradermal venom skin test is raised, and it is suggested that there is a need for caution and the use of serology as a supplementary diagnostic test.

SUMMARY

The important issue this year is the reminder that intradermal skin tests may be negative in venom-allergic patients, possibly because of changes in the potency of the extracts. The clinical history should drive the diagnosis of insect-sting allergy. When negative confirmatory venom skin-test or serology results are considered to be inconsistent with a positive history, they should be repeated.

Prevalence of pachycondyla chinensis venom allergy in an ant-infested area in Korea

Recently, immediate allergic reactions, including anaphylaxis, after Pachycondyla chinensis ant stings have been frequently reported in Korea. To estimate the prevalence of these reactions and the sensitization rate to P chinensis, we undertook a visit-questionnaire survey of the 327 adult residents living in a town in an ant-infested area in Korea. Skin prick tests with 6 common inhalant allergens, 3 bee venom allergens, and P chinensis whole body extract were performed on all ant-allergic subjects, on 86 asymptomatic residents, and on 37 controls outside the area. The serum-specific IgE to P chinensis extract was determined by ELISA. Seven subjects (2.1%) reported that they had experienced systemic allergic reactions to P chinensis stings; 4 of them had anaphylactic reactions. Large local reactions occurred in an additional 5 subjects (1.6%). All subjects with systemic allergic reactions had positive skin prick test results to P chinensis extract, whereas 23.3% of asymptomatic residents and 2.7% of the controls showed positive skin prick test results. The serum-specific IgE level was significantly higher in the subjects with systemic reactions than in the subjects with local reactions, the asymptomatic sensitizers, and the nonatopic controls. Sensitization to bee venom was found in 25% of the P chinensis -allergic subjects; this was significantly higher than the 3% rate seen in nonsensitized subjects. In conclusion, we report a 2.1% prevalence of systemic allergic reactions after P chinensis stings, based on self-reported symptoms, in an ant-infested area in Korea.