What is contact dermatitis?

Contact dermatitis is inflammation of the skin caused by direct contact with something that causes an irritation or allergic reaction. Given these two different causes, the condition can be broken down into two types: irritant contact dermatitis and allergic contact dermatitis. The irritant type is most common, accounting for at least three quarters of all cases of contact dermatitis.

Contact dermatitis is characterised by a red and inflamed skin rash. Contact dermatitis can occur anywhere on the body, but is most likely to appear on the hands and face.

Allergic reaction

A problematic physiological response to an allergen that comes into contact with the body.

Types

Irritant contact dermatitis

Irritant contact dermatitis occurs when the skin comes into direct contact with - and is irritated by - a particularly acidic or alkaline substance. Some common irritants include detergents, soaps, oils and solvents. These substances would cause inflammation in most people if exposure occurred frequently or over a long period of time.

Perhaps not surprisingly, irritant contact dermatitis occurs frequently on the hands. It is also common among certain types of workers, such as cleaners, mechanics, printers, hairdressers, builders and healthcare workers.

Allergic contact dermatitis

Allergic contact dermatitis occurs when the immune system reacts to an allergen. The immune system mistakenly damages normal tissue in an attempt to remove the allergen. This type of allergy is known as a delayed hypersensitivity reaction, as it takes days to develop. It is not a condition present from birth. Instead, contact with an allergen is required for a reaction to occur. In some cases, the allergy may not develop until years after initial exposure. However, once 'sensitised', the allergy is for life and the skin will react whenever it comes into contact with the allergen again.

Some substances will only cause an allergic reaction after they have been applied to the skin and are then exposed to sunlight. In these situations, the condition is known as photoallergic contact dermatitis.

Allergic reaction

A problematic physiological response to an allergen that comes into contact with the body.

Allergy

A harmful, hypersensitive immune reaction to usually innocuous environmental substances.

Immune system

The organs and cells involved in protecting the body against infection.

Acidic

Having characteristics of an acid, a substance with a sour taste and a pH of less than seven when dissolved in water, such as vinegar.

Alkaline

Having characteristics of an alkali, a substance that can neutralise acids and has a pH of greater than seven when dissolved in water, such as sodium bicarbonate.

Causes

Irritant contact dermatitis

Some examples of common irritants include:

  • Soaps, detergents and shampoos;
  • Perfumes and preservatives in cosmetics or toiletries;
  • Hair dyes;
  • Fabric softeners;
  • Solvents;
  • Machine oils;
  • Hard, chalky or heavily-chlorinated water;
  • Cement;
  • Pesticides and weed killers, and;
  • Rubber gloves.

Allergic contact dermatitis

Common substances and materials (allergens) that cause this condition include:

  • Cosmetics, such as hair dye, fragrances and nail polish;
  • Preservatives;
  • Rubbers, such as latex;
  • Metals such as nickel and cobalt found in jewellery, watch straps, zips, bra hooks, buttons and belt buckles;
  • Certain plants, such as poison ivy, poison oak, daffodils and tulips;
  • Adhesives, including those used in strapping tapes and eyelash glues, and;
  • Topical medications, such as antibiotics and corticosteroids.

Corticosteroids

A medication that resembles the cortisol hormone produced in the brain. It is used as an anti-inflammatory medication.

Risk factors

Risk factors for contact dermatitis include:

Family history of allergy

Allergic contact dermatitis is more likely to develop in people with a family history of other allergies.

Other skin disorders

Contact dermatitis is more likely to occur in people with another skin disorder, such as psoriasis, acne or eczema.

Certain occupations

Contact dermatitis is more likely to occur in people who regularly work outdoors, in the heat, or with their skin submerged in water. These environments tend to strip the skin of its protective oils.

Being female

Although women are more likely than men to develop contact dermatitis, this is not because of any biological or genetic factor. Rather, it is due to the fact that women more commonly fill occupations that involve exposure to irritants and allergens.

Exposure to sunlight

As certain substances only cause a skin reaction once exposed to sunlight, spending time outside may increase the likelihood of developing allergic contact dermatitis.

Allergies

A harmful, hypersensitive immune reaction to usually innocuous environmental substances.

Signs and symptoms

Contact dermatitis is most common on the hands and often first appears as skin dryness in the webbing between the fingers. However, the condition can develop anywhere on the body that has been exposed to an irritating substance. The signs and symptoms often depend on the cause and whether the dermatitis is due to an irritant or allergen.

Irritant contact dermatitis

When dermatitis is caused by an irritating substance, the main symptoms include:

  • Redness;
  • Burning pain;
  • Stinging;
  • Soreness;
  • A reaction that resembles a burn, and;
  • Dry, rough skin.

Symptoms usually appear within two days of having contact with the irritant and only in the direct area where the contact occurred. Strong irritants usually cause an immediate reaction, whereas reactions to mild irritants may require repeated or long-term exposure.

Allergic contact dermatitis

Symptoms of dermatitis caused by an allergic reaction include:

  • Redness;
  • A streaky or patchy rash;
  • Severe itching;
  • Scaling, and;
  • Blisters that may ooze or crust.

In cases of allergic contact dermatitis, symptoms may not appear until hours or days after contact with the inflammatory substance or material (allergen). While the symptoms generally appear in the area where contact occurred, sometimes the inflammation may occur on other areas of skin.

Red skin on hands, rash on hands, causes of rashes on hands, red blotchy skin.Visual appearance of contact dermatitis on hands. 

Allergic reaction

A problematic physiological response to an allergen that comes into contact with the body.

Methods for diagnosis

A doctor will generally diagnose contact dermatitis by looking closely at the skin and asking about symptoms, medical history and any family members with an allergy or skin condition. To identify any irritants or allergic causes that may be causing the condition, the doctor will probably also ask some questions about lifestyle and occupation.

In some cases, the doctor may swab the skin or take a small tissue sample (biopsy) to rule out other causes of inflammation.

Sometimes, contact dermatitis can be easily recognised and the cause identified without conducting any tests. However, when further investigation is required, the tests focus on applying potential irritants to the skin and observing the outcome.

Irritant contact dermatitis

Open application testing

To test for irritant contact dermatitis, the doctor may apply one or more common irritants to the skin on the forearm or inner elbow. After being left uncovered, the skin is then checked several times in the following days for a reaction. This method of diagnosis is known as open application testing.

In some cases, this process may be repeated on the same area of skin twice a day for 5-10 days, to see how the skin reacts. This is known as repeated open application testing (ROAT). If the symptoms are not too severe, a doctor may also suggest doing a similar test at home with cosmetics or personal care items thought to be causing a reaction.

Allergic contact dermatitis

Patch testing

If an allergic reaction is suspected, the doctor may refer you to a specialised skin doctor (dermatologist) for patch testing. During this test, very small amounts of different allergens are attached to the skin on the back or arms, using special tape. After two days, the dermatologist will remove the patches of tape and look for any signs of an allergic reaction. As most reactions take a few days to develop, the skin is usually examined again four to six days later.

Patch testing different allergens on the back.Patch testing of allergens. 

Allergic reaction

A problematic physiological response to an allergen that comes into contact with the body.

Allergy

A harmful, hypersensitive immune reaction to usually innocuous environmental substances.

Types of treatment

Both types of contact dermatitis generally clear over weeks or months if the cause can be identified and avoided. While there is no cure, one or more treatment options may be recommended by a doctor to reduce redness and itching. Treatments for both types include:

Self care

Initial treatment for contact dermatitis usually involves washing the affected area thoroughly with lots of water and then identifying the cause of the inflammation. After this has been done, a doctor may recommend leaving it to clear on its own, or another type of treatment to help ease symptoms.

Applying wet dressings or taking a cool bath may also be advised to provide relief from redness and itching. It may also help to choose smooth clothing and mild soaps without dyes or perfumes. To avoid scratching, some possible measures include keeping the nails short, wearing cotton gloves at night and covering the affected area with a dressing.

Emollients

Emollients are substances that soften the skin and keep it moist by covering it with a protective layer. As contact dermatitis causes skin dryness and cracking, adding moisture can prevent further irritation and water loss. Common emollients include paraffin preparations, sorbolene, aqueous creams and bath oils. A doctor will be able to suggest an appropriate option, as some emollients may irritate the skin further.

Corticosteroids

If the skin is particularly inflamed, a topical corticosteroid may be prescribed for application directly onto the skin. Corticosteroids are used to quickly reduce inflammation and are usually suggested in combination with use of an emollient. For mild to moderate cases, hydrocortisone or clobetasone butyrate may be prescribed. For cases that are severe or that do not respond to treatment, a stronger topical corticosteroid might be recommended. In rare cases, corticosteroids may be prescribed in oral tablet form, or as an injection.

Skin creams are used topically to alleviate contact dermatitis.Application of cream for treatment of contact dermatitis.  

Antihistamines 

Antihistamines help to relieve itching by suppressing part of the body's allergic response. Some of these medications are known as 'sedating antihistamines' because they also cause drowsiness. The most common type of sedating antihistamine is diphenhydramine.

Antibiotic medications

If contact dermatitis becomes infected with bacteria, antibiotics are usually prescribed in tablet or capsule form. The most common antibiotic for this type of infection is flucloxacillin, a member of the penicillin family of medications. In cases of penicillin allergy, erythromycin or clarithromycin may be used instead. Sometimes a topical antibiotic cream or ointment may be applied directly to the skin.

Light therapies

The most basic forms of light therapy involve exposing the skin to a controlled level of natural sunlight. More advanced options use ultraviolet light (UVA or UVB) to help control dermatitis. Care needs to be taken during these treatments to avoid overexposure to ultraviolet light, a known cause of skin cancers.

Allergy

A harmful, hypersensitive immune reaction to usually innocuous environmental substances.

Corticosteroid

A medication that resembles the cortisol hormone produced in the brain. It is used as an anti-inflammatory medication.

Potential complications

Generally, contact dermatitis symptoms can be managed effectively. However, complications may occur, particularly when itching and irritation are severe or ongoing. For example, continued scratching may break the skin or encourage oozing. Once the skin barrier has been broken, infection with bacteria or viruses becomes more likely.

Similarly, excessive scratching can cause a condition known as neurodermatitis (or lichen simplex chronicus). In short, scratching makes the area even more itchy, which leads to further scratching. Eventually this cycle causes the affected area of skin to become thick, leathery and discoloured.

For some people, severe or long-term symptoms may affect quality of life or result in psychological issues, such as distress, low self-esteem and embarrassment.

Prognosis

Generally, the outlook for contact dermatitis is quite good, with most cases clearing up within two to three weeks. However, it may return or become a long-term condition if the substance that caused it cannot be identified or avoided. If the cause is linked to employment, it may be necessary to leave that job or career.

On rare occasions, exposure to a substance that causes allergic contact dermatitis may cause a severe immune response, known as anaphylaxis. Urgent medical care should be sought if this occurs.

Contact dermatitis can also be embarrassing or interfere with sleeping, particularly when it is very itchy. Usually though, the condition can be managed by maintaining good skin care habits and avoiding the causes.

Prevention

The methods for preventing contact dermatitis closely mirror the self-care treatment options, particularly those relating to skin maintenance and avoiding triggers.

Contact dermatitis may be prevented by wearing protective clothing or gloves to reduce exposure in everyday situations. For buttons or fasteners that are attached to clothing, an iron-on patch over the item to prevent contact with skin could be considered. Similarly, if a certain product is causing a reaction, changing to one that does not contain the problem ingredient is usually recommended.

Applying emollients regularly, or using them in place of soap, can also help skin to heal and provide a protective barrier. This can help to prevent infection and worsening of symptoms.