Heat and Sweat

Overheating, sweating and sudden temperature changes are among the most commonly reported physical triggers of itch in Atopic Dermatitis. A typical example is coming in from the cold to a centrally heated room (Allergy UK). The NHS lists “heat or changes in temperature” among eczema triggers, and the National Eczema Association lists sweat, heat and humidity. Overheating in bed, running around and being over-dressed all count (Allergy UK). Sweat collects in the elbow and knee creases, the neck folds and under clothing. Japanese researchers suggest this pooling may help explain why toddler eczema settles in those sweat-prone flexures (Hiragun 2017). NICE CG57, however, records that the role of temperature extremes and humidity in causing flares is still unclear (see NICE CG57).

Heat and Sweat [triggers] Atopic Dermatitis Heat and Sweat [part-of] Environmental Triggers Heat and Sweat [worsens] Itch-Scratch Cycle

How sweat triggers eczema: irritant and allergen. Sweat left drying on eczematous skin irritates it through salt and moisture. Very occlusive ointments in hot, humid weather can block sweat ducts and cause sweat-retention dermatitis (Medscape). Sweat can also act as an allergen. About 80% of people with AD show an IgE (type I) reaction to their own sweat. The main antigen is MGL_1304, a protein made by the skin yeast Malassezia globosa that is secreted into sweat. It causes histamine release from the blood cells of most AD patients tested (Hiragun et al., JACI 2013). Levels of IgE against MGL_1304 are higher in AD than in controls, and the authors describe sweat as an aggravating factor “in all age groups” (Hiragun 2017). This “sweat allergy” research comes mostly from one Japanese group and largely from older patients. There is no routine test for it in toddlers, and it does not change practical advice.

Malassezia [causes] Heat and Sweat Heat and Sweat [relates] Th2 Immune Response

Summer flares. Seasonal patterns vary. Many children flare in winter from dry air and heating, while others flare in spring or summer with heat, sweat and Pollen (Bosma 2021, citing German and Japanese cohorts). Allergy UK notes that warm weather and sunshine help some people and worsen others. Sunscreens, needed for toddlers, may contain fragrance or preservatives that irritate, so it is best to stick with one product that is tolerated.

Heat and Sweat [relates] Pollen

Practical advice for toddlers. Keep rooms and the bedroom cool and at an even temperature, avoid over-bundling, and use lightweight, breathable cotton clothing and bedding. Wool and synthetics such as polyester and nylon cause overheating and sweating (Allergy UK; National Eczema Society; see Clothing and Fabrics). Rinse sweat off after hot play. In an observational study of 81 children aged 1–13 (mean 4.7 years), daily summer bathing with a mildly acidic cleanser, followed within 3 minutes by an emollient, improved SCORAD, itch and sleep. Children who skipped baths improved only in itch (Kim et al. 2012; see Bathing Frequency, Syndet Cleansers). An adult pilot study found showering, wiping or changing damp clothes helpful whether or not a sweat-allergy test was positive (Kaneko 2017). In hot weather a lighter cream may be more comfortable than a heavy ointment, which can trap sweat (Medscape; see Emollient Therapy).

Bathing Frequency [relates] Heat and Sweat Clothing and Fabrics [relates] Heat and Sweat

Connections

• Environmental Triggers — physical trigger, source: Allergy UK; NHS
• Clothing and Fabrics — synthetics and wool cause overheating, source: NES
• Malassezia — source of the main sweat allergen MGL_1304, source: Hiragun 2013
• Bathing Frequency — daily summer bathing removes sweat and lowers SCORAD, source: Kim 2012
• Emollient Therapy — occlusive ointments can cause sweat retention in heat, source: Medscape
• Pollen — spring/summer flare subgroup, source: Bosma 2021