What is Contact Dermatitis?
Contact dermatitis is a skin condition that looks similar to eczema, caused by certain chemicals or metals. These can either have a toxic impact without triggering an immune response (these are known as contact irritants), or react with proteins in your body causing an immune response (these are known as contact allergens).
We classify contact dermatitis into two types: irritant contact dermatitis and allergic contact dermatitis. Irritant contact dermatitis occurs when your skin reacts to a damaging chemical, causing inflammation. Allergic contact dermatitis occurs when your body produces a delayed immune response to foreign substances on your skin, and is dependent on the interaction of cytokines and T cells. In photo contact allergic dermatitis, rashes only appear on parts of your skin that are exposed to the sun, even though the allergen might be present on covered areas.
Until recently, it was thought that allergic contact dermatitis was uncommon. However, new data suggest that it is actually quite prevalent and affects almost 20% of children.
Fortunately, most cases of contact dermatitis resolve on their own and can be managed with simple care measures. Yet, for some people, the condition can persist and significantly impact their quality of life.
What Causes Contact Dermatitis?
Irritant contact dermatitis, a type of skin irritation, becomes more likely the longer and more intensely you’re exposed to a certain substance. Irritants can come in many forms, chemical or physical, causing skin irritation. Elements like friction from rough surfaces, minor skin injuries, the action of certain detergents, like sodium lauryl sulfate, can all cause irritant contact dermatitis. In fact, a combination of these often results in more cases than any of these factors alone.
The severity of this skin condition is dependent on several factors. These include the amount and concentration of the irritant, how long and how often you’re exposed to it. Skin type also plays a role; conditions like thin or thick skin, oily or dry, extremely fair complexion, previously damaged skin, or those with a genetic predisposition to certain skin conditions can affect the severity. Environmental factors, like extreme temperatures and humidity, also factor in.
Allergic contact dermatitis, on the other hand, is caused by common allergens such as nickel, balsam of Peru, chromium, neomycin, formaldehyde, thiomersal, perfume ingredients, cobalt, and parthenium. In the United States, poison ivy is thought to be the most common cause of this condition. About half to 70% of the adult population is sensitive to poison ivy or a similar plant, poison oak. When exposed to our skin, the allergen from these plants, urushiol, should be washed off as soon as possible using regular soap within a two-hour window to prevent reactions.
If the oil isn’t removed in time, potent skin creams may be used to reduce inflammation early on, within 12 hours of exposure. However, it’s important to note that less potent creams aren’t very effective, and even potent creams don’t significantly relieve symptoms once fluid-filled bumps have formed.
Risk Factors and Frequency for Contact Dermatitis
Irritant contact dermatitis often affects females, infants, the elderly, and those prone to allergies. It is common in workplaces, with up to 80% of job-related skin problems being irritant contact dermatitis.
Allergic contact dermatitis, on the other hand, can affect anyone. However, your age, job, and whether you have had atopic dermatitis (a type of skin inflammation) can increase your risk.
Contact dermatitis in general is most common in people with fair skin and red hair. Women are more likely to develop this condition due to the use of jewelry and fragrances.
Signs and Symptoms of Contact Dermatitis
Irritant contact dermatitis can cause symptoms like burning, itching, stinging, soreness, and pain, especially at the beginning. On the other hand, allergic contact dermatitis often brings about itchiness. Patients with a history of these conditions have a higher risk of developing nonspecific hand dermatitis and irritant contact dermatitis. Both irritant and allergic contact dermatitis can go through three stages of appearance.
- Acute phase: includes symptoms such as redness, swelling, oozing, crusting, tenderness, vesicles or pustules
- Subacute phase: this phase may present crusts, scales, and darker skin color
- Chronic phase: characterized by the thickening of the skin
Hands are the most common place to spot contact allergic dermatitis. There are no definitive signs and symptoms which can help to distinguish between allergic contact dermatitis and irritant contact dermatitis directly. In cases of irritant reactions, the peak of symptoms usually comes quickly, within a few minutes to hours following exposure, then starts to get better. With allergic contact dermatitis, symptoms usually appear 24 to 72 hours following exposure to the allergen and reach their peak about 72 to 96 hours later. Notably, allergic contact dermatitis takes a longer time to improve compared to irritant contact dermatitis, and it reoccurs quicker if exposure to the allergen happens again.
Common causes of allergic contact dermatitis include :
- Hair dye ingredients like Paraphenylenediamine (PPD) that often affect the scalp, face, and ears
- Neomycin and bacitracin used on areas of stasis dermatitis and leg ulcers commonly cause reactions on legs and feet
- Topical neomycin and corticosteroids may cause reactions in patients with outer ear infections
- Benzocaine applied in pruritus ani and pruritus vulvae can cause a reaction in women with lichen sclerosus et atrophicus
- Nickel, the most common metal in artificial jewelry, can cause reactions
Allergic contact dermatitis can also present different clinical patterns such as erythema multiforme, urticarial papular plaques, lichen-planus, lichenoid eruptions, purpuric petechial reactions, dermal reactions, lymphomatoid contact dermatitis, granulomatous and pustular reactions, pigmentation disturbances, or pemphigoid.
Testing for Contact Dermatitis
Understanding a person’s job, hobbies, and any medications they’re taking, whether topical (applied to the skin) or oral, is crucial to diagnosing contact dermatitis. To know the exact cause, a patch test is typically performed, which is considered the most reliable way to diagnose contact allergic dermatitis.
In patch testing, the doctor applies diluted chemicals found in everyday materials like metals, rubber, leather, preservatives, fragrances, toiletries, hair dyes, medicines, food, and drinks, among others. These chemicals are applied to a small area on the patient’s back to see if any of them cause a delayed allergic reaction.
These chemicals or allergens are placed in what’s called Finn chambers, which are then stuck to the patient’s back. After 48 hours, the patches are removed, and the reactions are assessed after another 24 to 72 hours. The reactions are graded from negative to extreme based on guidelines from the International Contact Dermatitis Research Group. The grading system is as follows:
- Negative (-)
- Irritant reaction (IR)
- Equivocal / uncertain (+/-)
- Weak positive (+)
- Strong positive (++)
- Extreme reaction (+++)
For patients allergic to nickel, a simple test can be performed at home on jewelry. A few drops of dimethylgloxime and hydroxide solutions are applied to the metallic surface of the jewelry with a cotton swab. If the jewelry contains nickel, the swab will turn pink.
Treatment Options for Contact Dermatitis
Avoiding the allergen that causes an allergic reaction is essential. This can be achieved by accurately identifying the allergen and wearing suitable clothes to protect yourself against irritants at home or work.
Strong skin creams like clobetasol propionate 0.05% cream can be used to lessen the swelling. It’s important to note that such powerful creams should not be applied on delicate skin areas like the face, genitals, or skin folds to prevent thinning of the skin. Medicines like hydroxyzine and cetirizine, known as antihistamines, can help manage itching. In severe cases, steroids that affect the entire body can be helpful but should be lowered gradually to prevent the reaction from coming back. Avoid things like rubbing, soap, perfumes, and dyes that could further irritate the skin. Skin moisturizers help to keep the skin hydrated.
Tacrolimus ointment and pimecrolimus cream are also useful in treating allergic skin reactions. These drugs change the immune response and help reduce inflammation by blocking an enzyme called calcineurin.
What else can Contact Dermatitis be?
Below is a simplified list of various skin conditions that could be confused with each other due to similar symptoms:
- Dry skin eczema
- Reaction to touch (Contact Urticaria Syndrome)
- Blistering skin problems caused by drugs
- Sensitivity to sunlight due to medicines (Drug-induced photosensitivity)
- Skin inflammation caused due to irritants (Irritant contact dermatitis)
- Separation of the nail from the nail bed (Onycholysis)
- Rash around the mouth and nose (Perioral dermatitis)
- Skin reaction to plants causing light sensitivity (Phytophotodermatitis)
- Ringworm of the body (Tinea corporis)
- A rare skin condition causing itchy, reddish-brown patches (Transient acantholytic dermatosis)
Each of these conditions show up in different ways on the skin, and a healthcare professional will need to examine the patient and understand their symptoms in order to provide the correct diagnosis.
What to expect with Contact Dermatitis
The outlook for patients with contact dermatitis, a type of skin inflammation, varies depending on the cause and the patient’s lifestyle. If the exposure to the irritant, the thing causing the reaction, can be avoided, the reaction will typically go away.
However, for patients who often come into contact with the irritant, such as wearing metal jewelry, or being around certain plants, the condition often lasts longer. It’s also common for the skin inflammation to come back again.
In the healthcare field, allergies to latex often cause contact dermatitis, and this can affect how healthcare is delivered. There have been reports of severe allergic reactions, known as anaphylaxis, due to contact with latex.