Allergic contact dermatitis to benzoyl peroxide mimics anaphylactic reaction

A 38-year-old women was referred to allergist doctor for a possible anaphylactic reaction to an ingredient contained in a topical antiacne gel, Cutacnyl® (Benzoyl peroxide 5%, Carbomère 940, Copolymère méthacrylique, Docusate sodique, Eau purifiée, Glycérol, Poloxamère 182, Propylèneglycol, Silice colloïdale anhydre, Sodium hydroxyde solution) (Galderma International, Paris, France).

On 3 April 2024, she had started a new topical antiacne treatment with a gel containing 5% benzoyl peroxide (BP) for acne. She began to experience facial pruritus on Day 2 and she stopped the treatment.

On Day 3, the patient experienced bright red erythema across her face with severe eyelid edema and strong pruritus (Figure 1A). She went to the emergency room due to the growing edema.

On the emergency report, a voluminous edema of eyelids, dysphonia, tachycardia and low arterial blood pressure were noted (Figure 1B,C). Suspecting anaphylaxis, the patient received an intramuscular adrenaline injection, an inhaled adrenaline spray, an intravenous antihistamine and intravenous corticosteroids. However, these treatments were not effective.

Emergency physicians also suggested bradykinin-induced angioedema. Diagnostic laboratory examinations for angioedema (serum levels of C3, C4 and C1INH) were normal.

In the emergency room, tryptase was also normal with a value of 3.26 μg/L, excluding anaphylaxis.

The reaction finally resolved in 1 week, with a desquamative rash.

She was then referred to allergy consulting in July 2024.

She mentioned she did not use any other topical treatments or cosmetics.

However, she had previously applied anti-acne creams, but could not remember which molecule she had used.

The patient applied Cutacnyl® all over her face, not just to the lesions as recommended by her general practioner. A prick-test to topical antiacne gel was performed and was negative at 20 min.

Patch testing was performed with the European and cosmetic series (Chemotechnique Diagnostics, Vellinge Sweden), BP 1% petrolatum and the Cutacnyl gel® (5% BP-containing) ‘as is’.

The haptens were applied on the back using IQ Ultra chambers (Chemotechnique Diagnostics), and following by an occlusion of 2 days, readings were performed on day (D)2 and D3.

Positive strong reactions were observed on D2 and D3 to BP 1% pet. (+++) and also, to topical antiacne cream as is (++) (Figure 2A,B).

A diagnostic of allergic contact dermatitis from BP was confirmed with an angioedema clinical aspect.

A positive patch test (+) reaction to nickel sulfate was found, relevant with reactions to costume jewellery in the past (Figure 2C).

ACD is a type IV hypersensitivity reaction which may also present as facial and eyelid edema.

Whereas anaphylaxis is a sudden IgE-mediated reaction occurring typically within 1–2 h, following contact with the allergen with several organ systems involved.¹ Anamnesis and clinical examination are essential to distinguish between the two kinds of reactions.

In our patient's case, she suffered with chronic low arterial blood pressure and tachycardia due to anaemia caused by thalassemia. She had a naturally deep voice. All drug treatment administered in emergency room was unnecessary and could have been iatrogenic, especially with intramuscular adrenaline injection.² However, in an emergency situation and due to a lack of available data, injecting adrenaline is appropriate.

Allergic contact dermatitis to BP is well known, since 1982.^3-7

BP is one of the most commonly prescribed for topical acne treatment.

BP is a powerful antimicrobial agent against Cutibacterium acnes (formerly named Propionibacterium acne), the primary pathogenic agent implicated in the development of inflammatory acne [Correction added on 23 December 2024, after first online publication: The bacteria name for Propionibacterium acne has been changed in this version.]. BP is also used in leg ulcer therapy and is employed in the chemical industry, as an initiator in free-radical-induced polymerisation of monomers to form plastics, and in the food industry, as a bleaching agent.

It is known that BP can caused severe angioedematous reaction without other typical signs of contact dermatitis.⁸ However, in our patient's case, the history was fairly typical, with a pruritic reaction on the second day, then a voluminous edema on the third day, and finally desquamation. Strong allergens are well known to cause angioedema of the face with intense pruritus, especially with the notorious paraphenylene diamine contact dermatitis.⁹

All practitioners need to know how to diagnose allergic contact dermatitis, even in the form of angioedema.

Magalie Coco-Viloin: Conceptualization; investigation; writing – original draft; writing – review and editing. Françoise Giordano: Validation; supervision; writing – review and editing.

The authors declare no conflicts of interest.

The patient's written consent was obtained.