House Dust Mites

House dust mites (mainly Dermatophagoides pteronyssinus and D. farinae) are microscopic arachnids. They live mostly in mattresses, bedding, carpets, curtains, soft furnishings and soft toys, and feed on shed skin flakes. The protein in their droppings triggers eczema in people who are sensitised to it. Mites need relative humidity above about 75%. They avoid light, and the highest numbers are found in carpeted bedrooms, sofas and beds, especially sheepskin bedding (DermNet). The most sensitising allergens are Der p 1/Der f 1, which are cysteine proteases, and Der p 2/Der f 2. Der p 11 is reported as a major allergen in Atopic Dermatitis specifically. Der p 1 can cut tight-junction proteins and so get through the skin directly (Agrawal & Woodfolk 2014), which links mites to Skin Barrier Dysfunction and the Th2 Immune Response.

House Dust Mites [triggers] Atopic Dermatitis House Dust Mites [worsens] Skin Barrier Dysfunction House Dust Mites [triggers] Th2 Immune Response House Dust Mites [part-of] Environmental Triggers

Sensitisation in eczema. Mite allergy matters for a subset of children, not everyone with eczema. The Cochrane review notes that as many as a third of people with eczema who test positive to house dust mite report worse eczema or breathing symptoms when exposed to dust (Nankervis et al. 2015). NICE CG57 says to consider inhalant allergy in children with seasonal flares, with eczema plus Asthma or Allergic Rhinitis, or aged 3 or over with eczema on the face, especially around the eyes. Testing is by Skin Prick Testing or specific IgE. NICE also says most children with mild eczema do not need allergy tests. High indoor humidity favours mites and mould (Lee et al. 2024).

NICE CG57 [relates] House Dust Mites Skin Prick Testing [relates] House Dust Mites House Dust Mites [relates] Allergic Rhinitis

Cochrane 2015: no clear benefit from avoidance. Nankervis et al. (Cochrane Database Syst Rev 2015, CD008426) included 7 RCTs with 324 adults and children. Only two trials were in children alone, and overall risk of bias was high. The interventions were mattress and bedding covers, more frequent or high-filtration vacuuming, and acaricide sprays. In one trial (n = 20), impermeable polyurethane mattress encasings plus acaricide spray gave no short-term benefit over cotton encasings plus placebo spray. One trial (n = 60) found a modest benefit over six months (SASSAD mean difference 4.2, 95% CI 1.7–6.7) for a package of mite-impermeable bedding, benzyltannate spray and high-filtration vacuuming. A third trial (n = 86) found no difference, and a fourth (n = 41) did not compare groups. No trial measured quality of life or adverse effects, and mite sensitisation did not change in any of the four trials that measured it. The authors concluded they were “unable to determine clear implications to inform clinical practice from the very low‐quality evidence”. The small benefits seen were in aeroallergen-sensitised people, so the value of these measures across all children with eczema “is unknown”.

Cochrane [contradicts] House Dust Mites House Dust Mites [relates] Atopic Dermatitis

Conflict: [National Eczema Society, n.d.] recommends practical mite reduction: washing bedding and soft toys at 60°C or more, weekly vacuuming, freezing non-washable toys for 24 hours, and considering hard flooring in severe eczema. [Nankervis et al., Cochrane, 2015] found no clear benefit from mite-reduction measures, including mattress covers, with very low-quality evidence; a modest benefit appeared only for a multi-component package in sensitised people. Unresolved — add to open_questions.

Practical measures and what parents report. National Eczema Society advice: wash bed linen at 60°C or more and tumble dry hot; vacuum weekly with a high-filtration, low-dust-exhaust vacuum, paying attention to seams; freeze non-washable cuddly toys in a bag for at least 24 hours, then brush them away from the child; and put a cotton sheet over carpet where a child plays. The NES says mites cannot be fully eradicated. Allergen immunotherapy for mite-sensitised eczema exists (DermNet cites Cochrane and RCT evidence) but is a specialist decision. Parent reports (evidence: anecdotal): in an r/eczema thread about a toddler with severe eczema, commenters suggested “she could have a dust mite allergy… they’re in even the cleanest houses”. One recommended replacing mattresses, buying encasings, washing everything at 60°C and removing carpets. These steps go beyond what the trial evidence supports. In r/toddlers, a parent who had moved to a hot, humid climate reported that their daughter turned out to be allergic to dust mites.

House Dust Mites [relates] Environmental Triggers

Connections

• Skin Barrier Dysfunction — allergen and protease that worsens the barrier, source: National Eczema Society; Agrawal & Woodfolk 2014
• Th2 Immune Response — Der p 1 breaches tight junctions, source: Agrawal & Woodfolk 2014
• Environmental Triggers — inhalant allergen trigger, source: NHS; NICE CG57
• Cochrane — avoidance review: no clear benefit, very low-quality evidence, source: Nankervis 2015
• NICE CG57 — when to suspect inhalant allergy, source: NICE CG57 1.4.1.3
• Skin Prick Testing — confirms mite sensitisation, source: NICE CG57; DermNet
• Allergic Rhinitis — shared aeroallergen, source: DermNet
• Atopic Dermatitis — Der p 11 major allergen in AD, source: DermNet