Early life exposure to allergens (including aeroallergens and ingested food allergens) may lead to allergic sensitisation and so potentially increase the risk of subsequent asthma, particularly in children at high risk (that is, children with a family history of asthma or atopy, particularly a parental history).

House dust mites

Exposure to high levels of house dust mite allergen in early life is associated with an increased likelihood of sensitisation to house dust mite by three to seven years of age.²⁸¹ Sensitisation to house dust mite is an important risk factor for the development of asthma, ²⁸², ²⁸³ and a few studies have suggested that exposure to high levels of house dust mites early in life increases the risks of subsequent asthma.²⁸⁴, ²⁸⁵

Pets in the home

A large number of birth cohort studies, longitudinal cohort studies and cross-sectional studies have addressed whether exposure to pets in the home in early life increases or reduces the subsequent risk of asthma and allergy, with contradictory results.

There is consistent evidence that being overweight or obese increases the risk of a subsequent physician diagnosis of asthma by up to 50% in children and adults of both sexes.³⁰⁹, ³¹⁰ A high birth weight is also associated with a higher risk of asthma.³⁰⁹

There is an increased risk of infant wheezing associated with maternal smoking during pregnancy which adversely affects infant lung function.^318-321

1. 281. Wahn U, Lau S, Bergmann R, Kulig M, Forster J, Bergmann K, et al. Indoor allergen exposure is a risk factor for sensitization during the first three years of life. J Allergy Clin Immunol 1997;99(6 Pt 1):763-9.
2. 282. Corver K, Kerkhof M, Brussee JE, Brunekreef B, van Strien RT, Vos AP, et al. House dust mite allergen reduction and allergy at 4 yr: follow up of the PIAMA-study. Pediatr Allergy Immunol 2006;17(5):329-36.
3. 283. Lau S, Illi S, Sommerfeld C, Niggemann B, Bergmann R, von Mutius E, et al. Early exposure to house-dust mite and cat allergens and development of childhood asthma: a cohort study. Multicentre Allergy Study Group. Lancet 2000;356(9239): 1392-7.
4. 284. Arshad SH, Bateman B, Matthews SM. Primary prevention of asthma and atopy during childhood by allergen avoidance in infancy: a randomised controlled study. Thorax 2003;58(6):489-93.
5. 285. Sporik R, Holgate ST, Platts-Mills TA, Cogswell JJ. Exposure to house-dust mite allergen (Der p l) and the development of asthma in childhood. A prospective study. N Engl J Med 1990;323(8):502-7.
6. 309. Flaherman V, Rutherford GW. A meta-analysis of the effect of high weight on asthma. Arch Dis Child 2006;91(4):334-9.
7. 310. Beuther DA, Sutherland ER. Overweight, obesity, and incident asthma: a meta-analysis of prospective epidemiologic studies. Am J Respir Crit Care Med 2007;175(7):661-6.
8. 318. Cook DG, Strachan DP. Health effects of passive smoking-10: Summary of effects of parental smoking on the respiratory health of children and implications for research. Thorax 1999;54(4): 357-66.
9. 319. Dezateau C, Stocks J, Dundas I, Fletcher ME. Impaired airway function and wheezing in infancy: the influence of maternal smoking and a genetic predisposition to asthma. Am J Respir Crit Care Med 1999;159(2):403-10.
10. 320. Gilliland FD, Berhane K, McConnell R, Gauderman WJ, Vora H, Rappaport EB, et al. Maternal smoking during pregnancy, environmental tobacco smoke exposure and childhood lung function. Thorax 2000;55(4):271-6.
11. 321. Lodrup Carlsen KC, Carlsen KH, Nafstad P, Bakketeig L. Perinatal risk factors for recurrent wheeze in early life. Pediatr Allergy Immunol 1999;10(2): 89-95.