Allergens in Common Brands of Clobetasol

Allergic contact dermatitis is a common diagnosis seen in the dermatologist’s office. Allergy to topical corticosteroid preparations should be considered when a patient does not respond to a treatment as anticipated or if a patient’s dermatitis worsens while using the corticosteroid. Patch testing is the gold standard in determining what the causative allergen may be, which can be the corticosteroid itself or one of the components of the vehicle. Delayed patch test reads are needed to ensure that a positive reaction isn’t missed, given the antiinflammatory component of the corticosteroid.

This study sought to find allergens in the common brands of clobetasol. The authors of the study found 49 different ingredients in 18 products. They identified 8.4 ingredients per product; 19 of the ingredients were considered as having allergenic potential, and there were, on average, 3.1 allergens per product. They identified the most common allergens as propylene glycol, isopropyl myristate, cetyl alcohol, and cetostearyl alcohol.

This article reminds us that prescriptions we use to treat dermatologic disease can sometimes exacerbate conditions if a patient is allergic to one of the ingredients. Although this study looked at brand names, we must also remember that most of our products can be generically substituted by the pharmacist unless we request the brand that is medically needed. So, when identifying someone with a specific allergen through patch testing, this must be considered when prescribing topical medications as these allergens can make their way into prescription products as well. Finding a brand name product that does not contain the allergen will require the designation of the brand as medically necessary; otherwise, you need to communicate with the pharmacist about the allergen that needs to be avoided in the generic products being dispensed.

I was disappointed by the article titled "Allergens in Common Brands of Clobetasol" and in the Journal of Drugs in Dermatology for doing a poor job of reviewing it.  Quite honestly, it gives the "peer-reviewed" medical literature a bad name because of easily verifiable factual inaccuracies. First, I will admit that there is no hard and fast rule for what is and is not a contact allergen. Is something that a single person, ever, has been reported allergic to considered a contact allergen? I suppose it technically is; but, for practical purposes, it is not. In my opinion, and I imagine in the opinion of most dermatologists, if a product is recommended for testing via inclusion on the American Contact Dermatitis Society Core Allergen Series, which was last updated in 2020, it is reasonable to consider it a contact allergen. Alternatively, I think we can safely assume that anything that is in the top 50 tested contact allergens in North America should be considered a contact allergen.

It was difficult for me to understand how the authors determined what is and is not a contact allergen. They list white petrolatum as a contact allergen, despite it being so rare as an allergen that it is used as the vehicle to test other allergens, but not cocamidopropyl betaine, which is not only recommended for testing but is the 43rd most common contact allergen in North America in the most recently released large dataset.

So, the big problem: The article lists Clobex and Clodan shampoos as being allergen-free. Per their package inserts, both contain cocamidopropyl betaine, a common, well-known allergen. Alternatively, it lists Temovate Scalp Solution as having two allergens. It has four ingredients, none of which are contact allergens: purified water, isopropyl alcohol, carbomer 934R, and sodium hydroxide — it is my go-to topical for a non-allergenic vehicle. If a reader looked at this article and wanted to minimize a patient's exposure to contact allergens, he or she would understandably stop recommending clobetasol solution (according to the article, it has two allergens!) and start recommending clobetasol shampoo (according to article, it has none!). This would be the exact opposite of what they were trying to accomplish and would harm patients.