Erythema-multiforme-like eruption following photoallergic contact dermatitis from oxybenzone

Drug-Induced Photosensitivity: Clinical Types of Phototoxicity and Photoallergy and Pathogenetic Mechanisms

Drug-induced photosensitivity (DIP) is a common cutaneous adverse drug reaction, resulting from the interaction of ultraviolet radiations, mostly ultraviolet A, with drugs. DIP includes phototoxicity and photoallergy. A phototoxic reaction is obtained when topical and systemic drugs or their metabolites absorb light inducing a direct cellular damage, while a photoallergic reaction takes place when the interaction between drugs and ultraviolet radiations causes an immune cutaneous response. Clinically, phototoxicity is immediate and appears as an exaggerated sunburn, whereas photoallergy is a delayed eczematous reaction. DIP may show several clinical subtypes. In this mini-review we report the pathogenetic mechanisms and causative drugs of DIP. We offer a detailed description of DIP clinical features in its classical and unusual subtypes, such as hyperpigmentation/dyschromia, pseudoporphyria, photo-onycolysis, eruptive teleangiectasia, pellagra-like reaction, lichenoid reaction, photodistributed erythema multiforme and subacute/chronic cutaneous lupus erythematosus. We described how physicians may early recognize and manage DIP, including diagnostic tests to rule out similar conditions. We made suggestions on how to improve sun exposure behaviors of patients at risk of DIP by means of an aware use of sunscreens, protective clothing and recent technologic tools. We highlighted the lack of sun safety programs addressed to patients at risk of DIP, who need a formal education about their condition.

Sunscreen Allergy: A Review of Epidemiology, Clinical Characteristics, and Responsible Allergens

Although allergy to sunscreen represents a small proportion (< 1%) of allergic contact dermatitis reactions in North America, it is one of the most common causes of photoallergy. The epidemiology and clinical characteristics of sunscreen allergy are summarized in this review. In addition, a detailed discussion of specific chemical sunscreen allergens is provided.

Sunscreen penetration of human skin and related keratinocyte toxicity after topical application

Sunscreen skin penetration and safety assessment should be considered together in order to ensure that in vitro cytotoxicity studies examine relevant doses of these organic chemical UV filters to which viable epidermal cells are realistically exposed. In this study, we sought to determine whether sufficient topically applied sunscreens penetrated into human viable epidermis to put the local keratinocyte cell populations at risk of toxicity. The penetration and retention of five commonly used sunscreen agents (avobenzone, octinoxate, octocrylene, oxybenzone and padimate O) in human skin was evaluated after application in mineral oil to isolated human epidermal membranes. Sunscreen concentration-human keratinocyte culture response curves were then defined using changes in cell morphology and proliferation (DNA synthesis using radiolabelled thymidine uptake studies) as evidence of sunscreens causing toxicity. Following 24 h of human epidermal exposure to sunscreens, detectable amounts of all sunscreens were present in the stratum corneum and viable epidermis, with epidermal penetration most evident with oxybenzone. The concentrations of each sunscreen found in human viable epidermis after topical application, adjusting for skin partitioning and binding effects, were at least 5-fold lower, based on levels detected in viable epidermal cells, than those appearing to cause toxicity in cultured human keratinocytes. It is concluded that the human viable epidermal levels of sunscreens are too low to cause any significant toxicity to the underlying human keratinocytes.

Photoallergic contact dermatitis

PURPOSE

To determine whether photoallergic contact dermatitis is as uncommon as it is usually considered to be and to review the associated clinical features.

METHODS

We reviewed the literature on photoallergic reactions induced by the topical contact of the skin with a chemical in the presence of, or followed by, exposure to UV or visible light. Some of the more recently observed photo-allergens and those presenting special clinical features are discussed.

RESULTS

The literature cites several topical substances that give rise to photoallergic contact dermatitis, some of them only exceptionally but others quite frequently. The clinical features are not always those of a eczematous eruption, and several parts of the body may be affected.

CONCLUSIONS

Many topical photoallergic culprits have been reported in the literature, the most important of which are sunscreen agents and, recently, non-steroidal anti-inflammatory agents (NSAIDs). Not at all exceptional is the occurrence of photoaggravation and recurrent transient or even persistent light reactions on previously exposed as well as non-exposed areas (often sparing the original application site), particularly with the NSAID ketoprofen. Moreover, cross-reactions with chemically-related as well as non-chemically related molecules are common. The potentially misleading clinical features observed in some cases, the diversity of the casual substances identified, and the low frequency with which photopatch testing is carried out in general indicate that the occurrence of photoallergic contact dermatitis might well be underestimated.

Facial erythema as a result of benzophenone allergy

Benzophenones are common causes of photoallergy and are increasingly used in products other than traditional sunscreens. Patients may be unaware of any sunscreen exposure when using a product such as shampoo containing benzophenone. Benzophenones also may produce photoallergic contact urticaria, in addition to delayed contact and photocontact dermatitis, which may complicate the clinical presentation. Allergy to benzophenone should be considered in the diagnosis of patients with patchy erythema of the face and neck that is not typically eczematous and that may otherwise be attributed to a rosacea diathesis, lupus erythematosis, or simple flushing. Patch and photopatch testing are indicated to evaluate these patients for allergy to benzophenone.

Percutaneous absorption of benzophenone-3, a common component of topical sunscreens

Benzophenone-3 (BZ-3) is a commonly used, chemical UV-absorber. It has been used for many years to protect against UV-radiation. Previous studies have shown that BZ-3 penetrates the skin, and it can be found in urine, faeces, and blood. In this study we examined the percutaneous absorption of BZ-3. The amount of BZ-3 absorbed was measured in urine, as experimental studies in the rat have shown that urine is the major route of excretion. Eleven volunteers applied the recommended amount of a commercially available sunscreen and urine samples were collected during a 48-h period after application. The average total amount excreted was 11 mg, median 9.8 mg, which is approximately 0.4% of the applied amount of BZ-3. Some of the volunteers still excreted BZ-3 48 h after application. It is evident that BZ-3 undergoes conjugation in the body to make it water soluble. However, we do not know at what age the ability to conjugate is fully developed, and therefore for children physical filters such as titanium dioxide and/or zinc oxide might still be considered a more appropriate sunscreen component.