Allergic Contact Dermatitis.

Allergic contact dermatitis is not curable in the sense that the sensitization is lifelong, but the disease is fully controllable with strict allergen avoidance. Once the allergen is identified by patch testing and removed from daily exposure, most patients remain symptom-free indefinitely. Re-exposure at any point — even decades later — can reproduce the original dermatitis within 24-72 hours, which is why ongoing avoidance is the key to long-term control.

Allergic contact dermatitis is itch-dominant, follows a 24-72 hour delay after re-exposure, requires prior sensitization, and produces sharply demarcated vesicular reactions. Irritant contact dermatitis is burning- or stinging-dominant, occurs in anyone given enough exposure without prior sensitization, has less sharply demarcated borders, and is patch-test negative. Both can coexist, so dermatology referral for patch testing is the only reliable way to tell them apart in chronic cases.

Patch testing is the diagnostic gold standard for ACD. Small chambers loaded with standardized allergens are taped to the upper back for 48 hours, then read by the dermatologist at days 2, 4, and 7. The procedure is painless, takes 30-60 minutes per visit, and identifies the offending allergen in roughly 70-80% of cases. Patients keep the area dry, avoid exercise and sun, and bring their own products to test.

The most common contact allergens worldwide are nickel (in jewellery and metal accessories), fragrance mix and balsam of Peru (in cosmetics and personal-care products), methylisothiazolinone (a preservative in liquid soaps and household cleaners), topical antibiotics neomycin and bacitracin, rubber accelerators (in gloves), p-phenylenediamine (in hair dye and black henna), and urushiol from poison ivy. The North American Contact Dermatitis Group publishes updated rankings every 2 years.

Yes. Sensitization can occur at any age and often develops in adulthood after prolonged or repeated exposure to a new product or workplace chemical. Common adult-onset sensitizations include hair dye, cosmetic preservatives, rubber accelerators in gloves, and topical medications used on broken skin. Once sensitization is established it is essentially lifelong.

An acute flare typically resolves over 2-4 weeks once the allergen is removed and topical corticosteroid is started. Visible redness drops within 3-5 days, itch within 5-10 days, and full clearance follows over the next 2-3 weeks. Chronic lichenified plaques take longer — 4-12 weeks of consistent therapy plus avoidance. Continued exposure perpetuates the rash indefinitely.

Eyelid skin is thin and absorbent, so it often shows allergic contact dermatitis to cosmetics, nail products transferred by the fingers, and hair products that drip onto the face. Common eyelid culprits include preservatives (methylisothiazolinone), fragrances, gold, and nickel in eyelash curlers. Patch testing identifies the trigger and a dermatologist can recommend safe alternatives.

Yes. Nickel is the single most common contact allergen worldwide. Roughly 17-19% of women and 3% of men patch-tested in the North American Contact Dermatitis Group 2019-2020 series reacted to nickel sulfate. Early ear piercing in childhood is the strongest risk factor, and once sensitization is established it persists for life.

No. The rash itself is not contagious. The urushiol oil from poison ivy, oak, or sumac is the trigger and can persist on skin, clothing, tools, and pet fur for weeks — that residual oil can transfer to another person and produce a rash, but the existing rash cannot. Wash skin, clothes, and tools with soap and water to remove urushiol.

Yes, topical corticosteroids are safe and effective when used correctly. Match potency to the site (low on face and folds, mid on body, high for thick plaques), apply once or twice daily during a flare for 2-4 weeks, and taper. Long-term continuous high-potency use on the face causes atrophy and rosacea, so calcineurin inhibitors are preferred for facial and eyelid maintenance.

Discuss workplace adjustments with your dermatologist and occupational physician. Options include substituting the allergen-containing product, using accelerator-free nitrile gloves with cotton liners, applying barrier creams pre-shift, and adjusting tasks. Where avoidance is impossible, structured topical and systemic therapy plus formal occupational disability assessment may be needed.

Yes. About 25-30% of patch-tested children show clinically relevant contact allergies, most often to nickel, fragrances, preservatives, and topical antibiotics. Black henna temporary tattoos applied to children can cause severe p-phenylenediamine sensitization with lifelong consequences for hair-dye use. Patch testing is well tolerated from school age onward.

For most patients, food does not drive ACD. A subset with proven systemic contact dermatitis to balsam of Peru or nickel may benefit from a targeted low-balsam or low-nickel diet under dietitian supervision when classic flare patterns are documented. Broad untested elimination diets cause nutritional gaps without reducing dermatitis.

Atopic dermatitis is a lifelong, flexural, itchy condition that usually starts in infancy with personal or family atopy. Allergic contact dermatitis often starts in adulthood, follows the contact pattern of the offending allergen, and is identified by patch testing. The two can coexist — atopic patients carry 1.5-2 fold higher risk of contact sensitization because of their disrupted skin barrier.

Not necessarily. 'Hypoallergenic' and 'natural' are unregulated marketing terms — many natural and botanical products contain potent fragrance and preservative allergens, including balsam of Peru, propolis, and tea tree oil. The only reliable safety check is to read the INCI ingredient list against your personal allergen list, using the ACDS CAMP app or SkinSAFE database.

In the United States, comprehensive patch testing typically costs USD 600-1500 out of pocket and is covered by most insurance plans when ordered by a dermatologist for chronic or refractory dermatitis. In the UK and Europe, patch testing is widely available through public health systems with no direct cost. In India and other emerging markets, panel testing is increasingly available at urban dermatology centres for INR 5,000-15,000.

Yes. Severe acute ACD can trigger autoeczematization (id reaction) — scattered papulovesicles on the trunk and limbs even where no allergen touched. Systemic contact dermatitis from oral or systemic exposure in a sensitized patient produces a symmetric flexural eruption known as baboon syndrome. Both resolve with allergen removal and anti-inflammatory therapy.

Seek same-day care if you develop generalized peeling with chills and fever (erythroderma), spreading honey-coloured crusting and fever (bacterial superinfection), sudden painful clustered vesicles with fever (eczema herpeticum), or severe periorbital swelling with eye pain or vision change. These complications can progress rapidly and need prompt hospital, antiviral, or antibiotic care.

Yes — this is called systemic contact dermatitis. A person already sensitized to a chemical on the skin can flare a generalized eczematous, dyshidrotic, or symmetric flexural rash when re-exposed orally or intravenously. Common triggers include metals (nickel), antibiotics, balsam-of-Peru-related compounds, and corticosteroids. Diagnosis is by exposure history plus patch testing.

Identify the allergen through patch testing, build a personalized avoidance plan with your dermatologist, verify every new product against the ACDS CAMP or SkinSAFE database, and maintain a daily fragrance-free emollient routine to support the skin barrier. Use accelerator-free nitrile gloves with cotton liners for wet work, and avoid black henna temporary tattoos and over-the-counter neomycin or bacitracin ointments.

Stress does not cause ACD but is a common flare amplifier. Stress releases neuropeptides that lower the itch threshold and disrupt the barrier, while sleep loss intensifies the itch-scratch cycle. Habit-reversal training, cognitive-behavioural therapy, and sleep hygiene reduce flare frequency in chronic disease.

Yes. Daily emollients, low-to-mid potency topical corticosteroids on small areas, and narrowband UVB phototherapy are considered safe in pregnancy. Topical calcineurin inhibitors are generally avoided. Oral retinoids (alitretinoin) and oral JAK inhibitors are contraindicated. Severe flares may need a short course of systemic corticosteroid after discussion with obstetrics and dermatology.