Symptomatic dermographism: wealing, mast cells and histamine are decreased in the skin following long-term application of a potent topical corticosteroid

Topical corticosteroids for hives and itch (urticaria): Systematic review and Bayesian meta-analysis of randomized trials

BACKGROUND

Topical corticosteroids are widely used as a treatment for itch and wheals (urticaria), but their benefits and harms are unclear.

OBJECTIVE

To systematically synthesize the benefits and harms of topical corticosteroids for the treatment of urticaria.

METHODS

We searched MEDLINE, EMBASE, and CENTRAL from database inception to March 23, 2024, for randomized trials comparing topical corticosteroids with placebo for patients with urticaria (either chronic spontaneous or inducible urticaria or acute urticaria elicited from skin/intradermal allergy testing). Paired reviewers independently screened records, extracted data, and assessed risk of bias. Random-effects meta-analyses addressed urticaria severity, itch severity (numeric rating scale; range 0-10; higher is worse), and adverse events. The Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach informed certainty of evidence ratings. PROSPERO registration: CRD42023455182.

RESULTS

A total of 19 randomized controlled trials enrolled 379 participants with a median of mean age of 30.1 (range 21.1-44.0) years. Compared with placebo, topical corticosteroids may reduce wheal size (ratio of means 0.47, 95% CI 0.38-0.59; low certainty) and itch severity (mean difference -1.30, 95% CI -5.07 to 2.46; very low certainty). Topical corticosteroids result in little to no difference in overall adverse events (94 fewer patients per 1000, 95% credible intervals 172 fewer to 12 more; high certainty).

CONCLUSION

Compared with placebo, topical corticosteroids may result in a reduction of wheal size and little to no difference in overall adverse events. Topical corticosteroids may reduce itch severity, but the evidence is very uncertain. Future large, randomized trials addressing the use of topical corticosteroids would further support optimal urticaria management.

Application of topical corticosteroids to sites of positive immediate-type allergy skin tests to relieve itching: results of a double-blind, placebo-controlled trial

BACKGROUND

In many allergy clinics topical corticosteroid cream is applied to sites of positive skin tests in an attempt to alleviate itching.

OBJECTIVES

To determine whether or not this practice is effective.

METHODS

Patients with 5 or more positive skin test results were randomly assigned to 1 of 3 groups after skin test result reading: application of 2.5% hydrocortisone in moisturizing cream, moisturizing cream alone, or no topical application. Immediately after the skin test results were read (baseline) and at 5, 15, and 30 minutes, patients rated their itching on a 100-mm visual analog scale.

RESULTS

Average itch scores for all groups combined were 44, 33, 22, and 12 at 0, 5, 15, and 30 minutes, respectively. No differences were found among the groups at any time point. No correlation was found between the baseline itch scores and age, sex, number of positive skin test results (> or = 3-mm wheals), or number of large positive skin test results (> or = 15-mm wheals).

CONCLUSIONS

The application of corticosteroid cream to sites of positive immediate-type allergy skin tests does not provide relief of itching; therefore, this practice should be abandoned. Instead, patients should be informed that any itching they may be experiencing will substantially resolve during the next 30 minutes and that application of such topical treatment will not hasten the relief of itching.

Prolonged topical application of tacrolimus inhibits immediate hypersensitivity reactions by reducing degranulation of mast cells

We studied the effects of prolonged topical application of tacrolimus on immediate hypersensitivity reactions. Tacrolimus, betamethasone or petrolatum was applied to the footpad of mice for up to 28 days after immunization, and the foot-swelling response to allergen was estimated. The reactions in tacrolimus-treated mice decreased significantly from day 14, while those in betamethasone-treated mice decreased significantly from day 7. Although the number of mast cells in the foot skin of each group did not differ significantly, the percentage of degranulated mast cells decreased in the tacrolimus-treated group on days 7 and 14. The TUNEL method indicated that there were no apoptotic mast cells in the foot skin of tacrolimus-treated mice. Continuous application of topical tacrolimus ointment may suppress immediate hypersensitivity reactions by reducing the degranulation of mast cells, rather than by decreasing their number.

Chronic Urticaria

Chronic urticaria is a common condition that can be very disabling when severe. A cause for chronic idiopathic urticaria (CIU) is only infrequently identified. Potential causes include reactions to food and drugs, infections (rarely) and, apart from an increased incidence of thyroid disease, uncomplicated urticaria is not usually associated with underlying systemic disease or malignancy. About one-third of patients with CIU have circulating functional autoantibodies against the high affinity IgE receptor or against IgE, although it is not known why such antibodies are produced, or how the presence of such antibodies alters the course of the disease or response to treatment. There are only a few publications relating to childhood urticaria, but it is probably similar to the adult form, except that adult urticaria is more common. The diagnosis is based on patient history and it is vital to spend time documenting this in detail. Extensive laboratory tests are not required in the vast majority of patients. Chronic urticaria resolves spontaneously in 30-55% of patients within 5 years, but it can persist for many years. Treatment is aimed firstly at avoiding underlying causative or exacerbating factors. Histamine H1 receptor antagonists remain the mainstay of oral treatment for all forms of urticaria. The newer low-sedating antihistamines desloratadine, fexofenadine, levocetirizine and mizolastine should be tried first. Sedating antihistamines have more adverse effects but are useful if symptoms are causing sleep disturbance. Low-dose dopexin is effective and especially suitable for patients with associated depression. There is controversy as to whether the addition of an histamine H2 receptor antagonist or a leukotriene antagonist is helpful. For CIU, second-line agents include ciclosporin (cyclosporine) [which is effective in approximately 75% of patients], short courses of oral corticosteroids, intravenous immunoglobulins and plasmapheresis, although the last two were found to be beneficial in small trials only. Treatments for CIU with only limited or anecdotal supportive evidence include sulphasalazine, methotrexate, stanazol, rofecoxib and cyclophosphamide. The efficacy of photo(chemo)therapy is controversial. Physical urticarias may respond to H1 receptor antagonists, although in delayed pressure urticaria, and cold, solar and aquagenic urticaria, the response may be disappointing. Second-line agents for physical urticarias vary depending on the urticaria and most have limited supportive evidence. The potential for spontaneous resolution, the variation in the disease activity and the unpredictable nature of the disease makes the efficacy of treatments difficult to assess.

Histamine: the quintessential mediator

Histamine is unique in being the only substance described to date which fulfils all of the criteria established by Dale for an inflammatory mediator. Thus, histamine is known to cause the "Triple Response" of Lewis and to act via H1 and H2 receptors to produce vasodilation and increased vascular permeability; elevated levels of histamine are found in inflamed tissue; histamine is produced and stored in mast cells and there are established mechanisms for histamine release via mast cell surface receptors; and antihistamines alleviate the clinical manifestations of histamine release. There have been several recent advances in our understanding of histamine pharmacology and of the pathomechanisms of chronic idiopathic urticaria (CIU), a disease in which histamine plays an important role. Two new histamine receptors have been identified, the inhibitory (H3) receptor and the intracellular (H(ic)) receptor involved in cell proliferation. There is now evidence that mast cell derived histamine release in patients with CIU is due to an autoimmune disease, mediated by autoantibodies to the alpha-subunit of the high affinity IgE receptor on mast cells and basophils. Removal of these autoantibodies by plasmapheresis, or treatment with intravenous immunoglobulins may cause clinical remission. Cyclosporin A has also been found to be of benefit to some patients with CIU probably due to a mast cell "stabilising" effect, leading to reduced release of histamine and other mediators. This article reviews our current knowledge on histamine, its role, receptors and mechanisms for release.

The effects of topical corticosteroids on delayed pressure urticaria

Six patients with delayed pressure urticaria (DPU) applied clobetasol propionate (0.05%) ointment or its base to predetermined test sites on the right and left thigh as part of a randomized, double-blind study. A pressure challenge was administered to each test site at the initial visit and repeated after 3 days and 6 weeks of treatment and at between 4 and 8 weeks after treatment. The areas of pressure-induced weals were measured 6 h after each challenge. At the 6-week visit, a 4-mm punch biopsy was taken from pressure-challenged skin on each test site. Sections were stained for mast cells and immunohistochemical labelling was used to demonstrate neutrophils (neutrophil elastase), eosinophils (eosinophil cationic protein), monocytes/macrophages (EBM 11), cells expressing the beta-2 integrins (CD11/18) and the vascular adhesion molecules, E selectin and intercellular adhesion molecule-1 (ICAM-1). In the steroid-treated sites, there was a significant decrease (P < 0.05, Wilcoxon's matched-pairs test) in the size of the pressure weals compared with baseline at 3 days, 6 weeks and at follow-up. Demonstrable mast cells were significantly decreased (P = 0.059) in the pressure-challenged areas in the steroid-treated sites compared with the base-treated sites. The histological response to pressure was minimal in both sites perhaps demonstrating an active pharmacological effect of the ointment base. In conclusion, the application of potent topical steroids significantly reduced the clinical response to pressure in patients with DPU, possibly through a reduction in mast cells.