Contact Dermatitis – Its Causes, Symptoms and Treatment
Contact dermatitis is a skin rash, skin irritation or skin inflammation caused by direct contact with a substance that triggers such reaction. There are two major types: allergic contact dermatitis and irritant contact dermatitis. Allergic contact dermatitis is caused by a normally harmless substance, which produces an exaggerated immune response whereas irritant contact dermatitis is triggered by exposure to a naturally irritating substance to human skin. Apart from the differences in origin, these two categories of contact dermatitis are clinically practically indistinguishable.
You may not experience symptoms of contact dermatitis the first time you are exposed to an offending substance. However, as you use or are exposed to the allergenic or irritable substance repeatedly, the skin becomes sensitized to it over time.
Types of Contact Dermatitis
Irritant Contact Dermatitis
Irritant contact dermatitis (ICD) accounts for approximately 80% of the cases of contact dermatitis. It is caused by exposure to a chemical that is naturally irritating to the human skin with hands being the most frequently affected area.
There are several forms of irritant contact dermatitis:
- Acute irritation is caused by a single exposure to chemicals such as noncorrosive acids and bases and strong solvents.
- Acute corrosion is caused by a single exposure to strong alkalis and acids.
- Cumulative irritation is the most common form, involving repeated exposures to substances, especially surfactants and emulsifiers. This form of ICD may be difficult to distinguish from ACD.
- Phototoxicity is caused by chemicals that only react when exposed to sunlight and its symptoms usually affect body areas most commonly exposed to sunlight. Such substances include sunscreens, shaving lotions, sulfa ointments and some perfumes.
Some people have skin that is more prone to irritant contact dermatitis. The person’s age, environment, genetics, underlying skin conditions, such as atopic dermatitis, and exposure to other chemicals are the major factors that determine susceptibility to ICD. Irritant contact dermatitis is also more likely in individuals with dry and light-colored skin.
Diaper rash happens to be the most common form of irritant contact dermatitis in children. It is caused by prolonged contact with natural substances present in the urine and stool. ICD can also be an occupational illness in adults of various professions. People whose household chores or hobbies involve irritating chemicals are also more likely to experience ICD.
Reddening of the skin is typical for mild cases of irritant contact dermatitis, but more severe cases may cause ulceration or swelling and resemble a burn. In contrast to allergic contact dermatitis, symptoms of ICD begin immediately after exposure to the irritating substance, or upon repeated exposure to it in the case of cumulative irritation.
Allergic Contact Dermatitis
Allergic contact dermatitis involves an immune system reaction when the skin is exposed to a substance the body regards as harmful. The skin reaction may not happen immediately, but within 24 to 48 hours or more after contact with an allergen. Allergic contact dermatitis can develop at any age, though adults develop it more often than children or the elderly.
ACD typically produces localized skin redness, severe itching and blistering, though the characteristics of the allergic reaction vary, depending on its cause. The initial exposure of the skin to the allergen does not immediately cause a rash. Instead, it sensitizes the skin. Once sensitized to a certain allergen, the body will repeatedly produce the symptoms of allergic contact dermatitis with each subsequent exposure to this substance. Sensitization can occur just after one single exposure to an offending substance or after several exposures. It is not uncommon to develop allergic contact dermatitis after many years of being exposed to a substance without any problems.
Potential Causes of Contact Dermatitis
When it comes to allergic contact dermatitis, a history of allergies or eczema increases the chances of developing this disorder. The presence of pre-existing irritable contact dermatitis can also lead to the development of allergic contact dermatitis. Moreover, cuts and other common skin wounds can contribute to ACD too by providing an entry point for allergens.
Common irritants and allergens causing contact dermatitis include:
- Contact lens solutions containing mercury
- Cosmetics and particularly hair dyes containing a substance called paraphenylenediamine (PPD)
- Detergents and soaps
- Fabrics and clothing
- Food additives
- Foods, particularly those high in nickel, mercury and cadmium such as fish
- Fruit, especially its peels
- Hair straighteners
- Jewellery and watches containing nickel, cobalt and other metals
- Latex found in gloves, condoms and rubber clothing
- Leather shoes treated with potassium dichromate
- Medications, particularly topical antibiotics or anesthetics
- Nail polish and nail polish remover
- Perfumes and sunscreens that contain preservatives or fragrances
- Plant oils from poison ivy, sumac, etc.
- Preservatives (e.g., formaldehyde)
- Ragweed pollen
Symptoms of Contact Dermatitis
Though the morphology of the two major types of contact dermatitis is similar, their symptoms may differ slightly. Whereas the symptoms of irritant contact dermatitis might be more spread out on the skin, the symptoms of allergic contact dermatitis tend to be confined to the area where the offending allergen touched the skin. Moreover, a rash caused by irritant contact dermatitis may appear immediately whereas a red rash resulting from allergic contact dermatitis may not appear until one to three days after exposure.
Irritant contact dermatitis is usually painful or burning rather than itchy, while allergic contact dermatitis tends to be very itchy. Irritant contact dermatitis frequently affects the hands, which have been directly exposed to the irritant and the face, particularly the eyelids. This form of dermatitis takes longer, often as long as a month, to resolve. If the rash does not improve or even continues to spread after a few days, patients should see their doctor. Worse than that, when the rash continues spreading, severe itching can be an indication of a serious condition and requires an immediate medical attention.
Symptoms of both types of contact dermatitis include:
- Feeling of warmth at the contact site
- Oozing fluid from contact site
- Skin thickening
- Tenderness of the skin in affected areas
Diagnosing Contact Dermatitis
A doctor will perform a physical examination and compile a thorough medical history, with special attention being paid to the patient’s history of allergic reactions. The appearance of the rash can help with diagnosis. Contact dermatitis rash often has clear-cut margins and acute angles. Since skin rashes associated with both forms of contact dermatitis start out looking the same, it is not always easy to determine whether it was caused by an allergen or an irritant. If the itchy rash and redness develop into blisters that form a crust or ooze, the condition is more likely to be diagnosed as allergic contact dermatitis than anything else. The location of the rash may also aid the doctor in determining the substance causing the dermatitis. For example, contact dermatitis on the neck may be triggered by chemicals contained in cologne or perfume.
Laboratory testing may not be necessary for mild forms of contact dermatitis that respond well to initial treatments. However, the laboratory tests used to diagnose more severe cases of contact dermatitis include:
- Patch testing introduces a suspect allergen to the skin to determine whether any allergic reaction occurs. It often is performed on patients who have chronic, recurring contact dermatitis.
- Skin lesion biopsy or culture examines a sample of skin taken from the site of irritation. This test cannot be used to identify the offending substance, but it greatly aids diagnosis by ruling out conditions that look similar to contact dermatitis such as fungal infections or psoriasis.
- Photopatch test is a specialized test used to diagnose photocontact dermatitis.
Prevention and Treatment of Contact Dermatitis
The most effective treatment for contact dermatitis is the avoidance of known irritating substances and allergens that cause it. Therefore, it is necessary to know what is causing the skin reaction. One of the most common protective measures for work-related contact dermatitis is wearing protective gloves in the workplace as well as at home if contact with known allergens or irritants is unavoidable. But be careful with latex gloves, as they are a common cause of contact dermatitis themselves. Vinyl gloves or cotton gloves worn over moisturizers are a better choice.
Other preventive measures involve the use of emollients to keep the skin moist and prevent itching. When it comes to diaper rash, the baby’s diaper should be frequently changed and a protective ointment applied. Other self-care measures that can be used to relieve the symptoms of contact dermatitis include:
- Applying cold compresses directly to the blisters.
- Applying calamine lotion in order to relieve itching.
- Applying over-the-counter hydrocortisone creams directly to the skin.
- Protecting the affected area from sunlight until the dermatitis has subsided.
- Taking cool oatmeal baths to soothe the skin. You should know, however, that oatmeal can be an allergen which can actually make the rash worse.
- Using moisturizers to help restore the normal texture of the skin but avoiding moisturizers containing nut oils.
- Washing with water and soap immediately after exposure to an allergen or irritant.
- Washing clothes that may have come into contact with the offending substance.
Medications for Contact Dermatitis
When it comes to medications, the first line of defence are non-prescription antihistamines used to treat common allergies. If over-the-counter antihistamines do not relieve the itching, the doctor may prescribe stronger antihistamines. Besides that, topical prescription corticosteroid medications may be applied to treat an inflammation in a confined area. These medications should be carefully used, as they can cause thin skin or rosacea. If the rash covers a large portion of the skin or is severe, corticosteroid pills or injections may be prescribed. Antibiotics may sometimes be needed to fight a secondary bacterial infection that develops at the site of the rash. Patients with chronic allergic contact dermatitis that cannot be controlled with the aforementioned measures may be treated with PUVA phototherapy.
Where to Get More Information: American Academy of Dermatology