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Causes of Skin Irritation: Environmental Factors & More

Skin irritation (irritant contact dermatitis) results from direct damage to the epidermal barrier. Allergic contact dermatitis involves a delayed hypersensitivity reaction. Both present with erythema, pruritus, burning, scaling, fissuring.

Major Categories

1. Environmental

  • UV Radiation: Sunburn (acute), photoaging, photosensitivity reactions.
  • Temperature Extremes: Cold (chilblains, frostbite), heat (miliaria, burns).
  • Wind/Low Humidity: Transepidermal water loss → xerosis, "winter itch."
  • Air Pollution: PM2.5, ozone, PAHs → oxidative stress, barrier disruption, inflammation.
  • Water: Hard water, chlorinated pools, frequent wetting/drying → barrier damage.

2. Chemical Irritants

  • Occupational: Solvents, detergents, acids/alkalis, cutting oils, cement, pesticides.
  • Household: Cleaners (bleach, ammonia), laundry detergents, fabric softeners.
  • Personal Care: Soaps (high pH), sulfates (SLS), alcohol-based toners, fragrances, preservatives (methylisothiazolinone), retinoids, AHAs/BHAs (overuse).

3. Biological

  • Plants: Poison ivy/oak/sumac (urushiol — allergic), stinging nettle (mechanical + chemical), giant hogweed (phytophotodermatitis).
  • Insects: Bites/stings (mosquito, bee, fire ant).
  • Microbes: Bacterial (impetigo), fungal (tinea, Candida), viral (herpes), parasitic (scabies).

4. Physical/Mechanical

  • Friction (chafing), pressure, occlusion (maceration), adhesive tape, shaving, scrubbing.

5. Systemic/Medical

  • Atopic dermatitis (intrinsic barrier defect + immune dysregulation).
  • Psoriasis, seborrheic dermatitis, contact urticaria.
  • Drug eruptions (morbilliform, fixed drug eruption, SJS/TEN).
  • Nutritional deficiencies (zinc, essential fatty acids, vitamins A, B2, B3, B6, C).
  • Systemic disease: thyroid, liver/kidney failure, malignancy.

6. Psychogenic

Stress → neurogenic inflammation (substance P, NGF), barrier impairment, scratching habit.

General Approach

  1. Identify & remove trigger.
  2. Gentle cleansing (syndet, pH-balanced).
  3. Barrier repair: Ceramides, cholesterol, fatty acids (CeraVe, Eucerin, Vanicream).
  4. Topical anti-inflammatories: Low-potency steroids (hydrocortisone 1%), calcineurin inhibitors (tacrolimus, pimecrolimus), PDE4 inhibitor (crisaborole).
  5. Oral antihistamines for pruritus (sedating at night).
  6. Patch testing if allergic contact dermatitis suspected.

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