Pigmented contact dermatitis - Skin
While some aspects of the etiology remain unclear, investigations, particularly in Japan, have found that the hyperpigmentation stems from sensitivity to certain chemicals in cosmetics. In these investigations, hundreds of patients were shown to have positive patch tests to cosmetics and their ingredients, and their hyperpigmentation significantly improved after avoiding cosmetics with those allergens. (The term "Riehl's melanosis" is actually a misnomer, because it refers to a pattern of hyperpigmentation identified in patients during World War I that is believed to have been caused by a dietary abnormality, whereas pigmented contact dermatitis is understood to be a form of allergic contact dermatitis.)
In contrast to a typical allergic contact dermatitis reaction, which presents with erythema, edema, and pruritus, pigmented contact dermatitis is mostly distinguished by hyperpigmentation and lacks the histological features of contact dermatitis such as spongiosis, which correlates with pruritus. Continuous daily exposure to low doses of allergens associated with this condition histologically produces liquefaction and degeneration of the basal layer of the epidermis, leading to pigmentary incontinence in the dermis with a lichenoid tissue reaction. Thus the inflammatory components of contact dermatitis are minimal while the pigmentary changes predominate. The pigment is so gradually absorbed that the hyperpigmentation is likened to a persistent "melanin tattoo." Treatment with corticosteroid ointments or even oral corticosteroids is essentially ineffective.
Common chemicals implicated in pigmented contact dermatitis include:
- Fragrances – hydroxycitronellal, benzyl salicylate, jasmine absolute, ylang-ylang oil, cananga oil, sandalwood oil, eugenol, cinnamic derivatives, and balsam of Peru
- Pigments – D & C Red 31, Red 225; D & C Yellow, No. 11 & 10; and pigments containing phenyl-azo-e-naphthol (PAN), aniline dyes, and kumkum (a red powder commonly used by Hindu women)
- Optical whiteners
- Coal tar derivatives, which increase photosensitivity
- Bactericidals – carbanilides like trichlorocarbanilide and Irgasan CF3
L81.4 – Other melanin hyperpigmentation
24285001 – Riehl's melanosis
- Allergic contact dermatitis – Presents with more prominent signs of erythema, urticaria, vesiculation, and pruritus. Caused by specific allergens; distribution varies and depends on contact.
- Irritant contact dermatitis – May have erythema, mild edema, and scaling caused by direct contact with chemical agents like corrosive agents, which can burn and produce ulcers; most commonly affects the hands.
- Berloque dermatitis (see phytophotodermatitis) – Hyperpigmentation in drop or pendant-like configuration in sun-exposed areas where perfume with bergamot oil (UV sensitizer) has been applied.
- Melasma – Brown-gray hyperpigmentation correlated mostly with sun exposure as well as genetics, pregnancy, hormone replacement therapy, oral contraceptives, and thyroid problems.
- Ochronosis – Bluish-black discoloration of various tissues like ocular tissue and ear cartilage; associated with exposure to various substances and alkaptonuria.
- Poikiloderma of Civatte – Common disorder, concerning mainly perimenopausal women; located on the lateral and low neck.
- Erythromelanosis follicularis of the face and neck – Reddish-brown pigmentation affecting follicles in the periauricular and maxillary areas; pigmented areas blanch with applied pressure, showing more brown pigment and telangiectases. Differing histology on skin biopsy.
- Addison's disease – Hyperpigmentation is more generalized on the body, with other systemic symptoms like hypotension, myalgias, arthralgias nausea, vomiting or diarrhea, and amenorrhea in women.
- Lichen amyloidosis – Extremely pruritic eruption of red-brown hyperkeratotic papules, distributed mostly on the shins, thighs, and feet; Congo red stain shows green birefringence with polarizing light.
- Macular amyloidosis – Symmetric and pruritic eruption of brown or grayish macules located on upper back and arms; same Congo red stain results as for lichen amyloidosis.
- Hyperpigmented lupus erythematosus – Direct immunofluorescence study on skin biopsy helps differentiate the two conditions.