Contact dermatitis

What it is

Contact dermatitis is an itchy or burning rash where a substance touched the skin. Irritant dermatitis comes from harsh things such as detergents and frequent hand washing. Allergic dermatitis is an immune reaction to substances such as fragrance, preservatives, nickel or hair dye (PPD).

How it works

There are two types. Irritant contact dermatitis is direct damage — a substance strips or injures the skin. Allergic contact dermatitis is an immune memory reaction: once sensitised, even tiny amounts of the allergen cause a rash 1–3 days after contact.

Why it matters on darker skin

On darker skin the rash may look dark, purple or greyish and can leave long-lasting dark marks. Black henna and some hair dyes contain PPD, a common and potentially severe allergen.

Causes and triggers

Irritants: soaps, detergents, frequent hand washing, solvents, harsh scrubs. Allergens: fragrance, preservatives (MI/MCI), hair dye (PPD, 'black henna'), nickel in jewellery and belt buckles, rubber, and some plants.

What helps — and why it works

Identify and stop the trigger. Wash the area with water, use a bland moisturiser and cool compresses. Patch-test new cosmetics and hair dye 48 hours before use. A doctor may prescribe a short course of an anti-inflammatory cream, or arrange patch testing to find the cause. Stop the suspected product: removing the trigger lets the barrier recover. Expected timeline: improves over 1–3 weeks. Bland emollient and soap substitute: rebuilds the barrier. Expected timeline: days. Patch testing by a doctor: identifies the exact allergen so you can avoid it for life. Expected timeline: results within a week of testing.

What to avoid and why

Avoid "black henna" tattoos, fragranced products during a flare and home remedies such as lime, alcohol or herbal pastes on the rash.

Common mistakes

• Switching to another product with the same allergen under a different name.
• Assuming 'natural' or 'hypoallergenic' means allergen-free.
• Using black henna tattoos.

Building a routine that lasts

Most skin problems improve with a short routine used every day rather than many products used occasionally. A practical base is a gentle cleanser, a fragrance-free moisturiser and a broad-spectrum sunscreen in the morning, with one targeted treatment at night. Introduce one new product at a time and give it two weeks before adding another, so that if your skin reacts you know the cause. Patch-test on the inner arm or behind the ear for a few days first. Skin renews itself roughly every four to six weeks, so most treatments need two to three cycles — eight to twelve weeks — before you can judge them fairly. Photographs taken in the same light every four weeks are more reliable than memory. In the Nigerian climate, heat, humidity and harmattan all change what your skin needs: lighter gels in the humid season and richer creams in dry months are both reasonable. If a product stings for more than a few minutes, causes swelling, or leaves new dark patches, stop it. Buy from registered pharmacies or official stockists, and use the Authenticity Check if you are unsure whether a product is genuine.

Reading labels and choosing products

On the label, look first for the active ingredient and whether the product is fragrance-free and non-comedogenic. Ingredients are listed in order of amount, so an active at the end of a long list may be present only in a small quantity. Be wary of products that promise results in days, that list no ingredients, or whose label is a sticker or handwritten. Words such as 'natural', 'herbal', 'organic' and 'dermatologist-inspired' are marketing terms, not safety standards. Hydroquinone, mercury compounds (sometimes listed as calomel or mercurous chloride) and strong steroids such as clobetasol do not belong in an over-the-counter cosmetic. A real NAFDAC registration number should be printed on the pack and should match the product on the official Greenbook register. Price is not proof: counterfeiters copy expensive brands. When in doubt, ask a pharmacist, keep your receipt, and use Melanin & Me's Authenticity Check and barcode scanner as a first screen.

Questions to ask your doctor or pharmacist

Useful questions include: What do you think is causing this? Is it likely to come back, and how can I prevent it? Which products should I stop? How long before I should expect improvement, and when should I come back if it isn't better? Are there side effects to watch for? Is this treatment safe if I am pregnant, breastfeeding or for my child? Writing your questions down, bringing your products (or photos of their labels) and taking dated photos of the problem make an appointment much more useful.