House dust mite allergy is a major cause for respiratory symptoms and sleep disorders in young children.

Sir,

We read with interest the paper by Sastry et al.[1] on the effect of indoor environment where sleeping with a stuffed toy was found to be associated with sleep disorders independent of wheeze in young children. The authors report the limitation of their study is that they did not collect information of how long these toys were used or whether they were cleaned during use, but they recognise well that build-up of dust mites leads to allergic rhinitis/asthma and subsequent sleep problems.[2] It has been estimated that 2 μg of Der 1 allergen of mite per 1 g of dust sensitises the host and 10 mg/g dust can invoke an asthma attack.[3] In vivo (skin prick) or in vitro (specific IgE) tests to aeroallergens such as dust mites, cockroach and weed/fungal pollens may have provided a better insight into the role of the indoor environment on wheeze and sleep-related symptoms in young children.

Our report using specific IgE tests on adults and children with persistent mild/moderate-severe rhinitis/asthma in the eastern part of the Indian subcontinent had shown that 60% of children were sensitised to dust mite allergens [Figure 1 and Table 1].[4] Almost half of the children were polysensitised [see Figure 1], with house dust mite, cockroach and common ragweed (c.f. Parthenium hysterophorus) allergens being the major sensitisers in these children. Consistent with our findings, Sastry et al.’s study also showed that existence of fungus in the indoor environment and regular dry dustings were associated with wheeze in the young children. A survey of dust mites in indoor homes of south Assam in 2011 found that 60% of beds, mattresses and pillows, 30% of upholstery and 10% of carpets were filled with dust mites.[5] Dey et al.’s review of house dust mites lists publications from 33 major cities of India where patients are sensitised to two or more major dust mites (Dermatophagoides pteronyssinus, Dermatophagoides farinae, Blomia tropicalis), with the highest sensitisation rate reported from West Bengal (80.3% D. pteronyssinus, 84.9% D. farinae).[67] Although our study did not specifically address sleep disorders, we found most parents complained of disturbed night sleep in their children due to coughing bouts or using bronchodilators for their children in early morning hours, which strongly suggests a link between allergic respiratory symptoms and sleep deprivation.

Figure 1

Pie chart showing aeroallergen sensitisation patterns among children

Table 1

Median IgE and specific IgE to four major aeroallergens in 30 children

Age range	2-12 years (mean age, 6.9 years)
Boys: girls	21:9
Total IgE range	From 12 to >5000 kU/L
Median IgE level	511 kU/L
Allergen	Median specific IgE level (range) kU/L	Number (% sensitised)
Dermatophagoides pteronyssinus	4.15 (from 1.29 to>100 kU/L)	18 (60%)
Dermatophagoides farinae	4.14 (from 0.67 to>100 kU/L)	18 (60%)
American cockroach	3.74 (from 0.45 to 11.5 kU/L)	11 (37%)
Common ragweed	0.73 (from 0.55 to 12.7 kU/L)	9 (30%)

The median and range of specific IgE level against aeroallergens reported refers to positive samples (≥0.35 kU/L were considered positive for all allergens, >100 kU/L was truncated to 100 for calculations)

Environment hazards of atmospheric pollutants, unrecognised allergy to animal dander (pets in the household) and positive family history of atopy put children at a very high risk of developing airways disease below the age of 10 years. Although members of the Pyroglyphidae family (D. pteronyssinus, D. farinae) are considered major mite allergens causing allergic disease, storage mites such as Acarus siro, Lepidoglyphus destructor and Tyrophagus putrescentiae are also becoming a problem across different cities in India. The burden of disease in Asia will only worsen with rapid urbanisation and climate change, and children will bear the brunt in the supposed comfort of poorly ventilated homes and stuffed toys.

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Conflicts of interest

There are no conflicts of interest.