Dermatitis is one of the most common skin conditions worldwide — yet it is widely misunderstood. This guide breaks down the science behind dermatitis: what it is, why it happens, how to recognise each type, and what treatments actually work.
What is Dermatitis?
Dermatitis is a general term for inflammation of the skin. It is not a single disease but an umbrella term covering several conditions that cause the skin to become red, itchy, swollen, and irritated. The word itself comes from the Greek derma (skin) and itis (inflammation).
Dermatitis is not contagious — you cannot catch it from touching someone who has it. However, it can significantly impact quality of life, causing chronic discomfort, sleep disturbance, and emotional distress, especially in children.
Types of Dermatitis
There are several distinct types of dermatitis, each with different triggers and mechanisms:
1. Atopic Dermatitis (Eczema)
The most common form, often starting in childhood. Linked to a genetic defect in the skin barrier protein filaggrin. Causes chronic itching, dry patches, and flare-ups. Strongly associated with asthma and allergic rhinitis — a triad called the "atopic march."
2. Contact Dermatitis
Triggered by direct skin contact with an irritant (irritant contact dermatitis) or an allergen (allergic contact dermatitis). Common triggers: nickel, latex, fragrances, detergents, and certain plants like poison ivy.
3. Seborrhoeic Dermatitis
Affects oily areas of the body — scalp, face, chest. Caused by an overgrowth of the yeast Malassezia. Presents as flaky, yellowish scales. Dandruff is a mild form of seborrhoeic dermatitis.
4. Dyshidrotic Dermatitis
Causes small, intensely itchy blisters on the palms, fingers, and soles. Often triggered by stress, sweating, or contact with metals such as nickel or cobalt.
5. Nummular Dermatitis
Characterised by coin-shaped patches of irritated skin. More common in older adults, often associated with dry skin and cold, dry weather.
What Causes Dermatitis?
The causes vary by type, but several factors are consistently involved:
- Genetics: Mutations in the FLG gene (encoding filaggrin) are a major risk factor for atopic dermatitis. A compromised skin barrier allows allergens and irritants to penetrate more easily.
- Immune dysregulation: In atopic dermatitis, the immune system mounts an exaggerated Th2 response, releasing inflammatory cytokines like IL-4 and IL-13.
- Environmental triggers: Pollen, dust mites, pet dander, mould, cold weather, and low humidity all worsen symptoms.
- Skin microbiome imbalance: Colonisation by Staphylococcus aureus is found in over 90% of atopic dermatitis patients and significantly worsens inflammation.
- Chemical exposures: Soaps, detergents, fragrances, and occupational chemicals are the primary triggers of contact dermatitis.
- Stress: Psychological stress stimulates mast cells and triggers inflammatory pathways, precipitating flare-ups.
Key Fact: Dermatitis affects approximately 15–20% of children and 1–3% of adults worldwide. In India, atopic dermatitis prevalence has been rising steadily, particularly in urban populations — possibly linked to reduced childhood microbial exposure (the hygiene hypothesis).
Recognising the Symptoms
Symptoms vary by type and severity but commonly include:
- Persistent itching — often worse at night
- Red to brownish-grey patches on skin
- Small, raised bumps that may weep fluid when scratched
- Thickened, cracked, or scaly skin (lichenification after chronic scratching)
- Swollen, tender skin following acute exposure to a trigger
- In seborrhoeic dermatitis: yellowish, greasy scales on the scalp or face
How is Dermatitis Diagnosed?
Diagnosis is primarily clinical — based on history and skin examination. Key diagnostic tools include:
- Patch testing: Gold standard for identifying contact allergens. Small amounts of common allergens are applied to the back under adhesive patches for 48–72 hours.
- Skin prick testing: Used to identify IgE-mediated allergens in atopic dermatitis.
- Serum IgE levels: Elevated total IgE suggests atopic background.
- Skin biopsy: Occasionally used to rule out other conditions like psoriasis.
Science-Backed Treatments
Topical Treatments
- Emollients (moisturisers): First-line treatment for all types. Restores the skin barrier, reduces water loss, and decreases flare frequency. Applied immediately after bathing.
- Topical corticosteroids: Anti-inflammatory; used during flares. Potency matched to body site — low potency on face, higher on limbs.
- Topical calcineurin inhibitors (tacrolimus, pimecrolimus): Steroid-free alternatives that suppress T-cell activation. Safe for face and skin folds.
- Antifungals: First-line for seborrhoeic dermatitis. Ketoconazole and selenium sulphide shampoos reduce Malassezia colonisation.
Systemic Treatments
- Dupilumab (Dupixent): A biologic that blocks IL-4 and IL-13 receptors. A major breakthrough for moderate-to-severe atopic dermatitis. Approved for use in children above 6 months.
- JAK inhibitors (upadacitinib, abrocitinib): Oral targeted therapies approved for moderate-to-severe atopic dermatitis in adults.
- Oral corticosteroids: Short-term use only during severe flares — not for long-term management.
- Antihistamines: Help manage itch, especially at night, though they do not treat the underlying inflammation.
Important: Never self-medicate with topical steroids without medical advice. Long-term misuse causes skin thinning (atrophy), striae, and — with potent steroids — systemic absorption effects. This is a significant problem in India where OTC steroid-containing creams are widely misused.
Lifestyle Management
- Bathe in lukewarm (not hot) water for no more than 10 minutes
- Apply moisturiser within 3 minutes of bathing ("soak and seal" method)
- Wear loose, breathable cotton clothing — avoid synthetic fibres and wool
- Use fragrance-free, hypoallergenic soaps and detergents
- Identify and avoid personal triggers (food, dust, pollen, stress)
- Keep nails short to minimise skin damage from scratching
- Use a humidifier in dry environments — aim for 45–55% indoor humidity
Key Takeaways
- Dermatitis is skin inflammation — not a single disease but a family of related conditions
- Atopic dermatitis involves filaggrin gene mutations and immune dysregulation
- Staphylococcus aureus colonisation significantly worsens atopic dermatitis
- Emollients are the cornerstone of all dermatitis management
- Dupilumab and JAK inhibitors represent major advances for severe cases
- Misuse of topical steroids is a serious and under-recognised problem