Allergic contact dermatitis (ACD) is a form of contact dermatitis which is a manifestation of an allergic response caused by contact with a substance; the other type is irritant contact dermatitis (ICD).
Although less common than ICD, ACD is accepted to be the most common form of immunotoxicity in humans. Due to its allergic nature, this form of contact dermatitis is an unusual hypersensitive reaction in the population. The mechanism by which these reactions occur is complex, with many levels of good control. Their immunological centers on the interactions of immunoregulatory cytokines and discrete subpopulations of T lymphocytes.
Video Allergic contact dermatitis
Signs and symptoms
The symptoms of allergic contact dermatitis are very similar to those caused by irritant contact dermatitis, which makes the former more difficult to diagnose. The first sign of allergic contact dermatitis is the presence of a rash or skin lesion at the exposure site. Depending on the type of allergen that causes it, the rash may discharge, drain or harden and may become raw, scaly or thickened. Also, it is possible that the skin lesions are not rash-shaped but may include papules, blisters, vesicles or even a simple red area. The main difference between rashes caused by allergic contact dermatitis and those caused by irritant contact dermatitis is that the latter tends to be limited to areas where the trigger touches the skin, whereas in allergic contact dermatitis the rash is more likely to be more widespread in the skin. Another characteristic of allergic contact dermatitis rash is that it usually appears after one or two days after exposure to the allergen, unlike irritant contact dermatitis that appears immediately after contact with the trigger.
Other symptoms may include itching, redness or inflammation, local swelling and the area may become more soft or warm. If left untreated, the skin may become dark and become rough and cracked. Pain can also be present.
Allergic contact symptoms can last for a month before completing completely. Once an individual has developed a skin reaction to a particular substance they will most likely have it for the rest of their lives, and the symptoms will reappear when in contact with the allergen.
Maps Allergic contact dermatitis
Cause
Common allergens involved include the following:
- Nickel (nickel sulphate hexahydrate) - has been recognized as a significant allergen. These metals are often found in cookware, jewelry and tongs or stainless steel clothing. Estimated estimates are currently around 2.5 million US adults and 250,000 children suffering from nickel allergies, which cost about $ 5.7 billion per year for symptomatic treatment. Most of the nickel allergies can be prevented.
- Gold (gold sodium thiosulfate) - precious metal is often found in jewelry and dental materials
- Peruvian Balsam (Myroxylon pereirae) - used in foods and beverages for flavorings, perfumes and toiletries for fragrances, and in pharmaceuticals and pharmaceutical goods for healing; derived from tree resin. It can also be a vanilla and/or artificial flavoring component.
- Chromium - used in tannery. It is also a component of cement/mortar, facial cosmetics, and some un-preserved bar soap.
- Urushiol - the oily layer of the Toxicodendron genus - poison ivy, poison oak, and poison sumac. Also found in mango and cashew nut plants.
- Sap from certain mangrove and agave species
- Thiomersal - a mercury compound used in local antiseptics and in vaccines
- Neomycin - a topical antibiotic common in first aid creams and ointments, cosmetics, deodorants, soaps, and pet foods. Found by itself, or in Neosporin or Triple Antibiotic
- A mixture of fragrances - a group of the eight most commonly found fragrance allergens in foods, cosmetic products, insecticides, antiseptics, soaps, perfumes, and dental products
- Formaldehyde - a preservative with many uses, for example , in paper products, paints, medicines, household cleansers, cosmetic products, and finished fabrics. Often released into the product using formaldehyde release such as imidazolidinyl urea, diazolidinyl urea, Quaternium-15, DMDM ​​Hydantoin, and 2-bromo-2-nitropropane-1,3-diol.
- Cobalt chloride - metals found in medical products; hair dye; antiperspirant; metal-lined objects such as buttons, buttons or tools; and cobalt blue pigments
- Bacitracin - a self-discovery topical antibiotic, or as Polysporin or Triple Antibiotic
- Quaternium-15 - preservatives in cosmetic products (self-tanners, shampoo, nail polish, sunscreen) and in industrial products (polishes, paints and waxes).
- Colophony (Rosin) - rosin, sap or sawdust usually from pine or spruce
- Topical steroids - see steroid allergy
- Photographic developers, especially those containing metol
- Topical anesthesia - such as pramoxine or diphenhydramine, after prolonged use
- Isothiazolinones - preservatives are used in many personal care, household, and commercial products.
- Mercaptobenzothiazole - on rubber products, especially shoes, gloves, and car tires.
- The soluble salt of platinum - see platinosis
Mechanism
ACD emerges as a result of two important stages: the induction phase , which forms and sensitizes the immune system to allergic responses, and the elicitation phase , where this response is triggered. Because it involves a cell-mediated allergic response, ACD is referred to as the Type IV delayed hypersensitivity reaction, making it an exception in the use of "allergic" designation, which usually refers to type I hypersensitivity reactions.
Contact allergens are essentially soluble haptens (low in molecular weight) and, thus, have a physico-chemical property that allows them to cross the stratum of the skin corneum. They can only cause their response as part of a complete antigen, which involves their association with epidermal proteins that form hapten protein conjugates. This, in turn, requires them to become protein-reactive.
The conjugate formed is then recognized as a foreign object by Langerhans cells (LC) (and in some cases other Dendritic cells (DC)), which then internalize proteins; transport through the lymphatic system to regional lymph nodes; and presents the antigen to T-lymphocytes. This process is controlled by cytokines and chemokines - with tumor necrosis factor alpha (TNF-?) And certain members of the interleukin family (1, 13 and 18) - and their actions work well to promote or inhibit the mobilization and migration of LC. When LC is transported to lymph nodes, they become differentiated and turn into DC, which is immunostimulant in nature.
Once in lymph nodes, differentiated DC presents the allergen-related epitope associated with allergens to T lymphocytes. These T cells then divide and differentiate, clonally clonal so that if allergens are experienced by individuals, these T cells will respond more quickly and more aggressively.
White et al. have suggested that there appears to be a threshold for the mechanism of allergic sensitization by ACD-associated allergens (1986). This is thought to be related to the degree to which the toxin induces increased regulation of the necessary cytokines and chemokines. It has also been proposed that vehicles in which allergens reach the skin can take some responsibility in epidermal sensitization by both helping percutaneous penetration and causing some form of trauma and mobilization of the cytokines themselves.
Memory Response
Once an individual is sensitive to allergens, future contact with allergens can trigger a reaction, commonly known as a memory response, on the original site of sensitization. So for example if a person has allergic contact dermatitis in the eyelid, say from the use of makeup, touching contact allergens with the fingers can trigger an allergic reaction to the eyelids.
This is due to T-cell localized skin memory, which remains at the initial sensitization site. In the same way, cytotoxic T lymphocytes patrol the skin and play an important role in controlling both viral reactivation (such as "cold sore" viruses) and in limiting replication when reactivated. The memory response, or "Reactivity Test", usually takes 2 to 3 days after contact with the allergen, and can last for 2 to 4 weeks.
Diagnosis
Diagnosing allergic contact dermatitis is mainly based on physical examination and medical history. In some cases, the doctor may establish an accurate diagnosis based on the patient's symptoms and the appearance of the rash. In the case of one episode of allergic contact dermatitis, this is all that is needed. Chronic and/or intermittent rashes that are not easily explained by history and physical examination will often benefit from further testing.
The patch test (delayed hypersensitivity allergy test) is a common examination used to determine the exact cause of allergic contact dermatitis. According to the American Academy of Allergy, Asthma, and Immunology, "patch test is the gold standard for the identification of contact allergens".
The outboard test consists of applying a small amount of potential allergen to a small patch and then placed on the skin. After two days, they are removed and if skin reactions occur on any of the substances used, the resulting bumps will be visible under the patch. The re-test is read at 72 or 96 hours after the application.
The patch test is used for patients who have recurrent chronic contact dermatitis. Other tests that can be used to diagnose contact dermatitis and rule out other possible causes of the symptoms include skin biopsy and culture of skin lesions.
Treatment
Clinical expression of dermatitis can be reduced by avoiding allergens. Through adherence to avoidance measures, the immune system may become less stimulated. The keys to avoid are proper evaluation and detection of allergens that are instigated. However, once the immune system registers allergens, its recognition is permanent.
The first step in treating this condition is proper recognition of clinical problems, followed by identification of the chemical causes and sources of the chemical. Corticosteroid cream should be used with caution and in accordance with the prescribed instructions because when used over time for longer periods, they can cause skin thinning. Also, in some cases such as poison ivy dermatitis calamine lotion and cold oatmeal bath can relieve itching.
Typically, severe cases are treated with systemic corticosteroids that can be gradually lowered, with various dosing schedules ranging from a total of 12 to 20 days to prevent a recurrence of the rash (while chemical allergens remain in the skin, up to 3 weeks, as well as topical corticosteroids, Tacrolimus ointment or pimecrolimus cream may also be used in addition to corticosteroid cream or, instead, oral antihistamines such as diphenhydramine or hydroxyzine may also be used in more severe cases to relieve severe itching, it is not recommended because there may be a second skin reaction (treatment of related contact dermatitis) of the lotion itself.
Other symptoms caused by allergic contact dermatitis can be reduced by a cold compress to stop the itching. It is critical to the success of the treatment that triggers are identified and avoided. Discomfort caused by symptoms can be lost by wearing finely textured cotton clothing to avoid frictional skin irritation or by avoiding soap with perfumes and dyes.
Generally, symptoms can disappear without treatment within 2 to 4 weeks but special medications can speed healing as long as the trigger is avoided. Also, this condition can become chronic if allergens are not detected and avoided.
References
Source of the article : Wikipedia
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