Allergic contact dermatitis due to neem oil: A case report and mini‐review

Abstract

omalizumab, she was in remission. However, 6 weeks after the last dose, both papular urticaria and hypohidrosis recurred. Restarting omalizumab cleared her symptoms. Her symptoms of atopic dermatitis were also ameliorated with regular use of topical corticosteroids.Cholinergic urticaria is a condition with papular wheals usually induced by heat and often accompanied by sweating disorder.The mechanism of how cholinergic urticaria associates with sweat disorder is not yet clear. There are several hypotheses regarding the pathophysiology of sweat disorder. One of them is that autoimmunity against the eccrine sweat glands causes malfunction of the sweat ducts, which results in sweat leakage into the dermis, followed by an allergic reaction due to the degranulation of mast cells. 1,2 Conventional treatment of cholinergic urticaria with corticosteroid or cyclosporin improved both skin and sweating symptoms in most cases. 3 Omalizumab is a therapeutic monoclonal antibody that neutralizes IgE by binding to the Fce3 domain of IgE. Omalizumab reduces the number of IgE receptors on the cell membrane, which suppresses the release of histamine. Therefore, omalizumab is labeled for the treatment of refractory chronic urticaria and bronchial asthma.Omalizumab has also been used successfully in the treatment of cholinergic urticaria. 4 To the best of our knowledge, this is the first case report of both urticarial papules and hypohidrosis being successfully treated with omalizumab.Patients who have an allergy to antigens against substances in sweat may experience edema by sweat leakage into the dermis. This local edema around the sweat duct may inhibit the flow. Thus, disappearance of wheals may instantly improve the patient's sweating function.Concomitant atopic dermatitis was also improved during omalizumab treatment. Cholinergic urticaria with sweat allergy is often associated with atopic dermatitis, and a common antigen in these two different diseases has been reported. 5 Omalizumab might have influenced both diseases in this patient. Further observation is needed.

Allergic contact dermatitis to neem oil used to treat a flare of atopic dermatitis

“…It is noteworthy that in previous reports, 75 control subjects were tested with neem oil ('as is', 25%-50% diluted, or 10% pet) with negative results. 1,[5][6][7][9][10][11] Neem oil is mainly constituted of fatty acids, including oleic, palmitic, stearic and linoleic acids, 5 but the precise sensitisers have not yet been identified. In one case, polysensitisation to argan oil, neem oil and glyceric extract of Mimosa Tenuiflora has been reported.…”

“…Previously, cases of ACD from neem oil have been published when used to treat alopecia, 4 furuncles, 5 dry skin, 6 facial acne, 7 and—in association with other oils or plant extracts—to treat psoriasis, 1,8 or as a fumigation agent for vegetable plots 9 . A case of ACD in a patient using neem oil to treat AD has also been previously reported, 10 as well as a case of occupational ACD in a worker who manufactured ‘natural’ soaps and creams 11 .…”

“…It is noteworthy that in previous reports, 75 control subjects were tested with neem oil (‘as is’, 25%–50% diluted, or 10% pet) with negative results 1,5–7,9–11 …”

“…Neem oil is mainly constituted of fatty acids, including oleic, palmitic, stearic and linoleic acids, 5 but the precise sensitisers have not yet been identified. In one case, polysensitisation to argan oil, neem oil and glyceric extract of Mimosa Tenuiflora has been reported 7 . Some allergenic molecules of these plant extracts, like triterpenes or phenols, might share a similar chemical structure, leading to cross‐reactions, even though independent concomitant sensitisation can probably not be ruled out.…”

A case of leukoderma probably caused by a soap containing neem oil

“…There have been seven reports of contact dermatitis caused by neem oil. 3,4 The absence of eczema and the patch test results indicated that her leukoderma was not postinflammatory depigmentation following contact dermatitis. In Japan, rhododendrol (RD)-induced leukoderma was confirmed in many individuals who had used RD-containing cosmetics in 2013.…”