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Introduction
Demographics
Causes
Clinical features
Variation in skin types
Complications
Diagnosis
Differential diagnoses
Treatment
Alternative names
Imidazolidinyl urea and DALU are formaldehyde-releasing preservatives used in many cosmetics and pharmaceutical preparations. They are commercially known as Germal 115 and Germal 11 respectively. Being structurally similar, cross reactivity between the two is common.
They are one of the most widely used preservative systems in the world and can be found in the following products:
Cosmetics
Self-hygiene/pharmaceutical products
Household and industrial products
An allergy to imidazolidinyl urea can develop in anyone. However, it is more common in:
Imidazolidinyl urea is not a common cause of contact allergy when compared with other preservatives. For this reason, imidazolidinyl urea is often the preservative found in products that are labelled ‘hypoallergenic’. However, if you have a sensitivity to imidazolidinyl urea, these products are far from being hypoallergenic and should be avoided.
The true incidence of allergies to imidazolidinyl urea is unknown but reportedly seen in 1.9-3.2% of patch-tested individuals.
Allergy to imidazolidinyl urea causes allergic contact dermatitis, a type IV hypersensitivity reaction. This mechanism involves CD4+ T-lymphocytes recognizing an antigen on the skin surface, which triggers the release of cytokines. These cytokines activate the immune system, leading to the development of dermatitis.
Allergy to imidazolidinyl urea typically presents with eczematous dermatitis localised to the site of contact. Skin lesions usually develop 48–72 hours after exposure and are generally confined to the contact area, though they may spread or become generalised.
The clinical features typically present in the following phases:
Symptoms include intense itching, which is the most commonly reported issue, along with burning pain and swelling in some cases. These symptoms typically arise within hours of contact and resolve within days if the skin is no longer exposed to imidazolidinyl urea.
Allergy to imidazolidinyl urea in darker skin tones may present as papulation, lichenification and pigmentary changes rather than erythematous patches and plaques. Furthermore, erythema may be disguised in darker skin tones (presenting as a grey or violaceous hue) resulting in delayed diagnosis.
Allergy to imidazolidinyl urea may result in the following complications:
Allergy to imidazolidinyl urea and DALU is diagnosed based on the clinical history and by performing special allergy tests, i.e. patch tests. Patch testing with 2% imidazolidinyl urea in petrolatum is used.
Self-testing a product for imidazolidinyl urea is possible but should be done only after first talking with your doctor. This should be done only with products that are designed to stay on the skin such as cosmetics (not including eyeliners or mascaras) and lotions.
Apply a small amount of the product to a small area of skin such as the bend of your arm twice a day for 1 week. Examine the area each day and if no reaction occurs, repeat the test on a small area in front of your ear. If no reaction occurs, it is unlikely you are allergic to it. Even so, you should still be cautious if you intend to use it over large areas as it may be an irritant.
Products such as shampoos and cleansers should not be tested in this way as they may cause an irritant contact dermatitis if they are covered or overused on tender areas.
Allergy to imidazolidinyl urea has the following differential diagnoses:
Allergy to imidazolidinyl urea can be prevented and treated using the following methods:
Prevention
If diagnosed with imidazolidinyl urea allergy then one should avoid exposure to imidazolidinyl urea-containing products. This can be achieved by the following methods.
Reading product labels:
Avoiding formaldehyde and related preservatives found in cosmetics, topical agents, and industrial fluids, such as:
Using safe alternatives (provided there is no known allergy to these), such as:
Treatment
Once dermatitis appears on the skin, treatment is as for any acute dermatitis:
Imidazolidinyl urea is also known by several other names. These include:
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