Propylene Glycol

An Often Unrecognized Cause of Allergic Contact Dermatitis in Patients Using Topical Corticosteroids

Mohammed Al Jasser, MD; Nino Mebuke; Gillian de Gannes, MD, FRCPC


Skin Therapy Letter. 2011;16(5) 

In This Article

PG and ACD to Topical Corticosteroids

The prevalence of ACD from topical corticosteroids (CS) is unknown. ACD to topical CS should be suspected if the dermatitis worsens or does not improve during treatment. ACD can result from an allergy to the steroid molecule or to a component of the vehicle. CS are divided into four classes on the basis of structure and cross-reactivity pattern: classes A (hydrocortisone type), B (triamcinolone acetonide type), C (betamethasone type), and D.[6] Class D is further divided into D1 (betamethasone dipropionate type) and D2 (methylprednisolone aceponate type). There are different screening markers that are used for patch testing to the corticosteroid classes. The screening markers used on the NACGD screening series are as follows: tixocortol-21-pivalate (class A), budesonide and triamcinolone acetonide (class B), clobetasol-17-propionate (class D1), and hydrocortisone-17-butyrate (class D2).[6] Patch test reactions to class A steroids are the most common.[7] Reactions to classes B and D steroids are less common, whereas reactions to class C steroids are extremely rare.[7] The most common cross-reactions are between steroids in classes A and D2, followed by classes B and D2, and classes A and B.[8]

An investigation by the NACDG demonstrated that topical CS were responsible for 18.3% of the positive patch test reactions to PG.[3] In a recent study, PG was found to be the most common allergen in topical CS, being present in 64% of the steroidal products.[7] It was especially common in branded ointments and gels. Moreover, studies have reported a significant number of patients have a concomitant reaction to both topical CS and PG, which suggests the possibility of cosensitization.[3,8]


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