found it on the net in eMedicine.com :
"Allergic contact dermatitis
Allergic contact dermatitis is a true delayed-type hypersensitivity reaction that occurs when a previously sensitized individual comes in contact with the allergen. Contact allergens are formed when a simple chemical of low molecular weight becomes complexed with a skin protein. Upon reexposure, an inflammatory reaction occurs.
In the acute phase, the skin is erythematous, edematous, and pruritic. Small, raised, circumscribed lesions (papules); weeping fluid-filled lesions (vesicles); exudation; and crusting are present. The lesions may become secondarily infected. In the chronic phase, the skin becomes thickened as a result of chronic rubbing or scratching. Thickening of the skin (lichenification), fissuring, and hyperpigmentation may also be observed.
Allergic contact dermatitis of the external ear is most commonly the result of hair products, cosmetics, earrings, hearing aids, topical medications, cell phones, and other objects that contact the pinna. Paraphenylenediamine, parabens, and quaternium-15, which are ingredients often found in shampoos, hair dyes, and hair sprays, commonly affect the conchae and periauricular regions. Hearing aids made of rubber, vinyl plastics, or methylmethacrylates or chemicals used to clean hearing aids may be the offending agents in cases of contact dermatitis of the external canal. Topical preparations, especially those that contain neomycin and related topical aminoglycoside antibiotics (eg, tobramycin, gentamicin) or topical anesthetic agents, such as benzocaine, may also affect the external auditory canal.
Earrings, especially those made of nickel, cobalt, palladium, or white or yellow gold, may cause dermatitis of the lobule.1 In Europe, a new initiative that calls for a reduction in the amount of nickel in commercial products was adopted following Danish studies that revealed a decrease in nickel allergy after a similar initiative was implemented in Denmark. Finally, lesions on the hemilateral pinna or the preauricular region may be the result of an allergy to chromium, a metal commonly used in cell phones.2
In each case, irritated, ulcerated, or inflamed skin appears to increase an individual's likelihood of becoming sensitized to an allergen. When a topical preparation is prescribed, underlying disease is often responsible for irritated inflamed skin within the external auditory canal, along the pinna, or both. Use of hearing aids may occlude the skin within the canal, promoting sensitization of products commonly used to make or to clean hearing aids. In a freshly pierced ear, haptenation is promoted if the dermis comes in contact with a substance such as nickel or gold. Gold sodium thiosulfate, a component of some earrings, has been shown to accumulate in the macrophages of susceptible individuals, resulting in a dense lymphocytic infiltration and pseudolymphoma formation. These pseudolymphomas may present as violaceous, nontender nodules found on ear lobes.
The diagnosis is made with the help of the patient's history and a patch or use test. Patch testing is usually performed on the back or arm and involves subdermal injection of small amounts of allergen. The skin is then observed for an inflammatory reaction. The use test involves the removal of all possible offending agents and the reintroduction of those agents, one at a time, at approximately a 3-day interval, until a reaction is provoked and the allergen is identified. In addition to these 2 tests, a thorough workup includes potassium hydroxide preparation, fungal cultures, Gram stain, and bacterial cultures to exclude a superimposed infection.
In rare instances, a skin biopsy may be performed to identify the lesion. Histopathologic evaluation reveals a dense lymphocytic infiltration with a few eosinophils and plasma cells in the dermis and subcutaneous tissues and lymphoid follicles with germinal centers. T-cell lymphocytic infiltration, especially around blood vessels, is seen in one variant, known as "lymphomatoid contact dermatitis." Clinically and histologically, this can mimic mycosis fungoides and may be considered in the differential diagnosis. Other potential differential diagnoses include irritant contact dermatitis, seborrheic dermatitis, psoriasis, atopic dermatitis, dermatophytosis, infectious eczematoid dermatitis, discoid lupus erythematosus, and angiolymphoid hyperplasia.
Treatment involves avoidance of the offending agent. Silicon hearing aids, which are hypoallergenic, may be substituted in the case of a hearing aid allergy. Using stainless steel earrings until the earring tract has epithelialized adequately may prevent an allergic reaction to earrings. Three weeks is usually appropriate for epithelialization. Cool saline or astringent compresses, topical corticosteroids, aluminum acetate, Burow solution, or Lassar paste can be used for treatment of symptoms. Promptly treat secondary infections with the proper antibiotics. Recent animal studies suggest that blocking IL-18 and IL-12 may be beneficial in the treatment of allergic contact dermatitis."
It may be a good idea to have a chat with a dermatologist if at all concerned, esp if you are to go ahead with the piercing
all the best, rue
