Sofa dermatitis refers to a persistent skin allergy that occurs in people who have bought leather sofas, couches, and other upholstered furniture pieces containing dimethyl fumarate (DMF), an anti-molding agent. This manifests as eczematous rashes and in some cases, serious chemical burns. In all cases, it is linked to the presence of Chinese-made leather furniture treated with an antifungal chemical.
First reported in 2007, hundreds of people have been diagnosed with this condition so far, and at least one fatality has been suspected. The epidemic spread to many countries in the EU and to the US and Canada as well, however the EU has since banned the use of DMF in consumer products.
Leather furniture exported after manufacture in China is packed with sachets of the potent antifungal, DMF. This is deemed necessary to keep the leather dry and mold-free during transit and storage in humid warehouses.
However, DMF is known to evaporate from the sachets, seeping into the leather and transferring on to skin and clothing. It is a powerful irritant and allergen, producing a type IV (delayed) hypersensitivity reaction, even in miniscule amounts. It is responsible for causing skin ulceration or blistering. In addition, skin rashes and conjunctivitis have also been reported as a result of exposure to DMF.
Many patients complain that their symptoms are not relieved with cessation of direct exposure i.e., after selling or disposing of the treated furniture. Apparently, the volatile chemical can remain in the air and deposit on the furniture. It then penetrates it to reach the skin when someone sits on the sofa, chair, or couch. Some individuals have extreme hypersensitivity to DMF. Some items of clothing and footwear are also known to contain DMF sachets.
In most cases, the patient develops skin lesions of an eczematous nature, most commonly on the back, the buttocks, the posterior of the thigh, and the back of the arm. The weeping lesions tend to persist despite treatment with topical corticosteroids.
The etiology of the condition was pinpointed by specific allergy tests performed with thin layer chromatography. The chemical present in a chair upholstered with suspected fabric was used for patch testing and produced positive reactions in all the patients who had furniture-related dermatitis, unlike the other chemicals extracted from the covering fabric using gas chromatography-mass spectrometry techniques. The sensitized patients were also likely to show cross-reactions to other allergenic chemicals used in the upholstered furniture industry. DMF is able to produce strongly positive allergic reactions on the skin at dilutions down to 0.01.