Contact Dermatitis

Introduction | Aetiology and Risk Factors | Clinical Presentation | Diagnosis | Management and Treatment | Prevention | When to Refer | References

Introduction

Contact dermatitis is a type of inflammatory skin condition that occurs when the skin comes into contact with an irritant or allergen, leading to redness, itching, and sometimes blistering. It can affect people of all ages and is classified into two main types: irritant contact dermatitis and allergic contact dermatitis. While often manageable with topical treatments and avoidance of triggers, severe cases may require more intensive management.

Aetiology and Risk Factors

Contact dermatitis can be caused by a variety of substances that either irritate the skin or trigger an allergic response:

1. Irritant Contact Dermatitis (ICD)

• Irritants: Common irritants include soaps, detergents, solvents, acids, alkalis, and prolonged exposure to water. These substances can damage the skin barrier, leading to irritation and inflammation.
• Risk Factors: People with occupations that involve frequent hand washing, handling chemicals, or exposure to wet work (e.g., healthcare workers, cleaners, hairdressers) are at higher risk of developing ICD.

2. Allergic Contact Dermatitis (ACD)

• Allergens: Common allergens include nickel (found in jewellery), fragrances, preservatives (e.g., in cosmetics), rubber (latex), and certain plants like poison ivy. ACD occurs when the immune system reacts to a substance that the skin has become sensitised to.
• Risk Factors: Individuals with a history of atopy (e.g., eczema, asthma, hay fever) may be more prone to developing ACD. Sensitisation can occur at any time, even after years of exposure to a particular substance.

Clinical Presentation

The presentation of contact dermatitis varies depending on the severity of the reaction and whether it is irritant or allergic in nature:

• Redness (Erythema): The affected area appears red and inflamed, often with well-defined borders where the skin came into contact with the irritant or allergen.
• Itching: Itching is a common symptom, and in allergic contact dermatitis, it may be intense.
• Swelling and Blistering: In more severe cases, the skin may develop blisters that can ooze and crust over, particularly in allergic contact dermatitis.
• Dryness and Scaling: Chronic exposure can lead to dry, scaly patches of skin, especially in irritant contact dermatitis.
• Cracked Skin: Repeated exposure to irritants can cause the skin to crack, leading to pain and an increased risk of secondary infections.
• Location: The rash typically appears on the hands, face, or other exposed areas, depending on the type of exposure. The distribution may provide clues to the cause (e.g., a rash under a watchband suggests an allergic reaction to nickel).

Diagnosis

Diagnosis of contact dermatitis is primarily clinical, based on history and examination, but may sometimes require further testing:

• History: A detailed history of recent exposures, occupation, hobbies, and any new products or materials that have come into contact with the skin is crucial for identifying potential triggers.
• Physical Examination: Examination of the affected area can help differentiate between irritant and allergic contact dermatitis, based on the pattern and appearance of the rash.
• Patch Testing: Patch testing may be conducted to identify specific allergens in cases of suspected allergic contact dermatitis. Small amounts of potential allergens are applied to the skin under adhesive patches, and reactions are observed after 48-96 hours.
• Differential Diagnosis: Other conditions to consider include atopic dermatitis, psoriasis, seborrhoeic dermatitis, and fungal infections, which may present with similar symptoms.

Management and Treatment

Management of contact dermatitis involves identifying and avoiding triggers, treating inflammation, and preventing recurrence:

1. Avoidance of Triggers

• Identify and Eliminate Triggers: Once the cause of contact dermatitis is identified, the key management strategy is to avoid exposure to the irritant or allergen. This may involve changing skincare products, wearing protective gloves, or avoiding certain metals.
• Substitute Products: Recommend hypoallergenic and fragrance-free products to minimise the risk of future reactions. For occupational exposures, suggest the use of barrier creams or protective clothing.

2. Topical Treatments

• Topical Corticosteroids: Topical steroids are the mainstay of treatment for reducing inflammation and itching. The potency of the steroid should be matched to the severity of the dermatitis and the location of the rash. For example:
  • Hydrocortisone 1%: A mild steroid, suitable for sensitive areas like the face and for children.
  • Betamethasone valerate 0.1%: A moderate to potent steroid, often used for more severe cases or on thicker skin areas like the palms and soles.
• Emollients: Regular use of emollients helps to restore the skin barrier, reduce dryness, and prevent flare-ups. Non-fragranced, hypoallergenic emollients are recommended.
• Topical Calcineurin Inhibitors: For sensitive areas where long-term steroid use is a concern, tacrolimus or pimecrolimus may be prescribed as a steroid-sparing option.

3. Oral Treatments

• Oral Antihistamines: Antihistamines can help control itching, especially in allergic contact dermatitis. Non-sedating options like cetirizine or loratadine are preferred during the day, while sedating antihistamines like diphenhydramine can be helpful at night.
• Oral Corticosteroids: In severe cases, short courses of oral corticosteroids (e.g., prednisolone) may be necessary to control widespread inflammation, particularly in allergic contact dermatitis.

4. Supportive Care

• Cool Compresses: Applying cool, wet compresses can help soothe inflamed skin and reduce itching.
• Skin Protection: Educate patients on protecting the skin from further irritation, such as by wearing gloves when handling irritants and avoiding scratching the affected areas.

Prevention

Preventive strategies are crucial for managing contact dermatitis, particularly for those at high risk:

• Avoid Known Irritants and Allergens: Patients should be educated on avoiding substances that have previously caused reactions. This includes reading labels on skincare products and household items.
• Protective Measures: Encourage the use of protective gloves, clothing, and barrier creams in occupations or situations where exposure to irritants or allergens is unavoidable.
• Skin Care Routine: Advise a simple, gentle skincare routine using hypoallergenic and fragrance-free products to maintain the skin barrier and reduce the risk of dermatitis.

When to Refer

Referral to a dermatologist may be necessary in the following situations:

• Severe or Refractory Cases: If contact dermatitis does not respond to standard treatments, or if the condition is severe, referral to a specialist for further evaluation and management is advised.
• Uncertain Diagnosis: If the diagnosis is unclear or if the presentation is atypical, a dermatologist's input may be required to rule out other conditions.
• Need for Patch Testing: In cases of suspected allergic contact dermatitis where the allergen is not easily identified, referral for patch testing can help determine the specific cause.

References

1. British Association of Dermatologists (2024) Guidelines for the Management of Contact Dermatitis. Available at: https://www.bad.org.uk (Accessed: 26 August 2024).
2. National Institute for Health and Care Excellence (2024) Contact Dermatitis: Diagnosis and Management. Available at: https://www.nice.org.uk/guidance/ng104 (Accessed: 26 August 2024).
3. British National Formulary (2024) Topical and Oral Treatments for Dermatological Conditions. Available at: https://bnf.nice.org.uk/ (Accessed: 26 August 2024).