Dimethyl fumarate (DMF) is a white crystalline powder, which is packed in sachets to protect leather goods like recliners, sofas, couches, or armchairs, against mold attack.
However, DMF is also a potent irritant and sensitizer, which is capable of causing acute and severe contact irritation in addition to skin allergy following exposure to it. The symptoms typically comprise an itchy, scaling or papulovesicular rash, which is reddened and swollen. The areas affected are commonly the back, the posterior aspect of the legs and the arms, and the buttocks - all of which come into contact with the furniture.
If an individual develops an acute and intransigent skin reaction which is not easily treated, and which does not yield a positive reaction to any of the available commercial patch tests, DMF allergy should be considered among other differential diagnoses.
Once the cause of the rash is confirmed to be DMF, the patient needs to remove the source of exposure from the premises promptly. Following cessation of exposure, the acute dermatitis should be treated with topical corticosteroids to alleviate the inflammation and allergic reaction rapidly. Emollients are useful to soften the skin and ease the scaling.
In some cases the allergy is more severe, or is complicated by irritant contact dermatitis. These patients require hospitalization for systemic steroid therapy, and sometimes antibiotics for secondary infection.
The linking of DMF to several hundred cases of severe skin irritation and allergy led to a ban on its use inside the European Union, as well as on the import of any products which use DMF. Such a ban has not been introduced yet in the US or in Australia, or in Asian countries.
Individuals who show hypersensitivity to DMF should be aware that leather furniture, and up to a quarter of all leather footwear bought in some of these countries, contains the chemical.
Such people should avoid touching or using all products with the potential for DMF contamination. This may be tricky because the agent is not always clearly labeled. Some names to watch out for include ‘mold inhibitor’ or ‘anti-mold’, or even ‘silica gel’, especially in footwear. The latter may be mixed with DMF without being labeled as such.
The name of the compound itself may take several different forms, such as fumaric acid, dimethyl ester, allomaleic acid dimethyl ester, dimethyl (E)-butenedioate, or methyl fumarate.
Again, shoes which contain DMF should be allowed to air for several months before one wears them. However, very sensitive individuals should avoid such shoes altogether, because it is possible that the chemical has already seeped into the leather. For these items, the period required for DMF to fully evaporate is measured in years rather than in months.
Finally, people who have recently bought a new item of clothing or furniture and develop an otherwise inexplicable skin rash must consider DMF allergy to be a possible cause.