What Is Allergic Contact Dermatitis?

Contact dermatitis is an inflammatory reaction that occurs on the skin or mucous membrane after a single or multiple exposures to an exogenous substance at the site of contact or beyond. Showed as erythema, swelling, pimples, blisters and even bullae.

Basic Information

English name
Visiting department
Common locations
Common symptoms
Erythema, swelling, pimples, blisters, bullae

Causes of contact dermatitis

The etiology can be divided into two types: primary stimulus and allergy. Primary irritant contact dermatitis The contact has strong irritation to the skin. Anyone can develop dermatitis after contact, which is called primary irritation. There are two types of primary irritation, one is very irritating and develops a short time after exposure; the other is weaker and develops a long-term exposure, such as soap and organic solvents. Allergic contact dermatitis The contact is basically non-irritating. After a few people are sensitized by contact with the substance, they contact the substance again. After 12 to 48 hours, dermatitis occurs in and around the contact site.
There are many substances that can cause contact dermatitis, mainly animal, plant and chemical.

Clinical manifestations of contact dermatitis

Dermatitis is generally non-specific. Due to different contact materials, contact methods, and individual responses, the form, scope and severity of dermatitis are different. In mild cases, it is locally erythema, reddish to bright red, slightly edema, or dense papules at the tip of the needle. In severe cases, erythema is swollen. On this basis, there are most papules and blisters. Bullae can occur when the inflammation is severe. Ruptured blisters include erosion, exudate, and crusting. If it is a severe primary stimulus, it can cause epidermal necrosis and fall off, and even deep dermal ulcers. When dermatitis occurs in loose tissues, such as eyelids, lips, foreskin, scrotum, etc., swelling is obvious, showing limited edema without clear edges, shiny skin, and disappearing surface texture.
The location and scope of dermatitis are consistent with the contact area of the contact object, and the realm is very clear. However, if the contact object is gas or dust, the dermatitis is diffuse without a clear boundary, but it mostly occurs in exposed parts of the body.
Most of the subjective symptoms are itching and burning or pain, and a few severe cases may have systemic reactions such as fever, chills, headache, nausea, and so on.
The course of the disease is self-limiting. Generally, after the cause is removed, it is properly treated and can be cured in 1 to 2 weeks. Repeated exposure or improper handling can turn into subacute or chronic dermatitis with reddish-brown mossy or eczema-like changes.
Irritant contact dermatitis can manifest itself as erythema, blisters, or exudation in the acute phase. Subacute and chronic can manifest erythema, rough, desquamation, and cleft palate. Depending on the nature of the irritant and the length of exposure, it can clinically manifest as acute irritant dermatitis, delayed acute irritant dermatitis, irritant reactions, cumulative irritant dermatitis, pustular irritant dermatitis, and mechanical stimulus-induced dermatitis. Wait.

Contact dermatitis diagnosis

According to the history of contact, acute dermatitis with a clear state suddenly occurs at the contact site or exposed body part. The rash is mostly a single form. The skin lesions quickly disappear after removing the cause, and it is easy to diagnose. When the cause is unknown or in contact with several kinds of contact objects, and the cause needs to be found, a patch test can be performed.

Contact Dermatitis Treatment

The cause of contact dermatitis is closely related to the contact. The first treatment is to find out the cause of the allergy, avoid re-exposure to the substance, and treat the symptoms that have appeared.
1. Find the cause of allergies
Take a detailed medical history, and carefully inquire about the environment related to the onset, the type and quantity of the substances contacted, the physical and chemical properties, the length of contact, the method of contact, and any similar rashes in the past. From the medical history to analyze which substances may be related to provide a basis for skin patch test. Once the cause of the allergy is found, try to avoid re-exposure.
Irritants or toxic substances that remain on the skin should be washed away as soon as possible, and water, physiological saline or fresh soapy water can be used for washing. If the contact is a strong acid, it can be washed with a weakly alkaline liquid (such as soda water); if it is a strong alkaline substance, it can be washed with a weakly acidic liquid (such as boric acid).
2. Avoid irritation
When clinical symptoms appear, local irritation should be minimized. Avoid scratching, scalding with hot water, and avoid strong sunlight or hot air stimulation.
3. Systemic treatment
Oral antihistamines, such as cyproheptadine, diphenhydramine, chlorpheniramine, atorvastin, cetirizine, mizolastine, ebastine, desloratadine, etc .; large doses Vitamin C is administered orally or intravenously; 10% calcium gluconate injection, intravenous bolus. Glucocorticoids can be given to patients with a wide area and severe erosion and exudation. For example, oral prednisone, triamcinolone, or dexamethasone; intramuscular injection of depotrazone. Severe cases can also be treated with hydrocortisone or dexamethasone intravenously. After the symptoms are alleviated, they can be maintained orally.
If contact dermatitis is accompanied by local infections, such as lymphangitis, lymphadenitis, and soft tissue inflammation, antibiotics can be used. The lighter ones are given roxithromycin, penicillin potassium, cephalexin or sulfa drugs. The severe cases are given intravenous penicillin , Cephalosporins or quinolone antibiotics.
4. Local treatment
Local treatment is very important and should be treated separately according to clinical manifestations.
(1) In the acute stage, those with erythema and pimples as the main body should use lotion, cream or ointment. Such as calamine lotion, shaking lotion, triamcinolone cream, clofluxone cream, skin cream, etc., can also be used with pine oil, bran oil, zinc oxide ointment. The swelling is obvious. Those with blisters, erosions and exudates can do open cold and wet compresses. The wet compress solutions are 3% boric acid solution, 1: 2 aluminum acetate solution, 1: 8000 potassium permanganate solution. If there is purulent secretion, use 0.02% furacicillin solution or 0.5% ethacridine solution for wet dressing. Wet compresses should not be too long, usually 2 to 3 days of wet compresses. When the exudate stops and the swelling subsides, stop the wet compresses and use a cream or ointment for external application.
(2) In the subacute or chronic stage, creams and ointments are mainly used externally. Corticosteroid ointments can be used, as well as pine oil ointment, black bean paste, zinc oxide ointment, etc. If purulent secretions are available, Add antibiotics such as neomycin, erythromycin, bacitracin, or other bactericides such as mupirocin ointment, berberine, mercury, etc. into the ointment.


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