Causes of Dermatitis

Dermatitis - eczema - is skin inflammation with an itch at its centre. It is not one disease but a pattern, and the causes split into what touches the skin from outside and what stirs it from inside.

From the outside (contact causes)

• Irritants: soaps, detergents, dish-washing liquids, sanitizers, solvents, frequent wet work - they strip the skin's protective oils directly. The housewife's hand eczema and the mechanic's forearms are classic
• Allergens: nickel (jewellery, jean buttons), fragrances, preservatives in creams and cosmetics, hair dye (PPD), rubber, cement chromate, certain plants - the immune system reacts specifically, and patch testing can prove it
• Weather and water: cold dry winters, hot sweaty summers, hard water - all stress the skin barrier

From the inside

• Atopy: the inherited tendency - people with eczema often have or develop asthma and allergic rhinitis (the "atopic march"); the skin barrier protein filaggrin is often genetically weaker
• Stress and poor sleep: genuine triggers - the itch-scratch cycle feeds on both
• Hormonal shifts, sweating, wool and synthetic fabrics against the skin
• Stasis: poor leg veins pool fluid and inflame the skin of the lower legs in older adults

What is NOT a cause

• Dermatitis is NOT contagious - no one catches eczema from touch, sharing towels or swimming pools. The visible rash carries no infection to others
• It is not caused by "impure blood" or bad hygiene - if anything, over-washing worsens it

One-line summary

Dermatitis comes from outside (soaps, nickel, fragrances, weather) and inside (the inherited atopic barrier, stress, stasis) - it is never contagious, and finding YOUR triggers is half the treatment.