Is there a link between smoking during pregnancy and allergic rhinitis in the offspring?

Allergic rhinitis in offspring

Allergic rhinitis, also known as allergic rhinitis, is a common chronic inflammation of the nasal mucosa (i.e. rhinitis) and is mediated by immunoglobulin E (i.e. antibody responsible for allergies). It is estimated that allergic rhinitis affects 10% to 25% of the human population globally. Typically, the disease manifests in early childhood and can lead to decades of impaired quality of life. Classic symptoms of the disease closely associated with asthma would be:

• Itching of the nose and eyes
• Sneezing
• Rhinorrhea and nasal congestion
• Watery eyes

Not only active smoking, but also passive smoking as an environmental factor can be linked to allergic rhinitis. A meta-analysis published in 2014 found an association between passive smoking in the general population and the risk of allergic rhinitis in non-pregnant women. According to this study, the amount of smoke produced is thought to pollute the surrounding air, increase allergens, and irritate the mucous membranes with harmful cigarette components such as formaldehydeor acrolein. Subsequently, vasospasm (i.e., spasmodic constriction of blood-bearing vessels) and contraction of the rhinitis occurs - which in turn (with long-term exposure) can lead to disruption of the hair cells in the nose. This can cause allergic rhinitis. As current studies have not been able to show clear results regarding tobacco exposure and its risks within the uterus of a pregnant woman, a team of researchers has now used a meta-analysis to investigate the link in the offspring.

Epigenetic link

The meta-analysis, published in 2021 in the Journal Medicine, examined relevant literature in channels such as SinoMed, PubMed, and Web of Science, and performed extensive quality assessment, data extraction, and data analysis. The following criteria were applied for inclusion or selection:

1. Study type: cohort, case-control, or cross-sectional.
2. Primary outcome was allergic rhinitis in offspring, with physician diagnosis, skin prick test (i.e. allergens are dripped on the skin, then that site is scratched) or International Study of Asthma and Allergy in Childhood (ISAAC) questionnaires.
3. Exposure to tobacco was smoking (active and passive) by the pregnant mother.
4. The studies included enough data on risk estimates with odds ratio (i.e. odds ratio) and range of expectation (i.e. confidence intervals) or their calculation.

Results

A total of 1,149,879 samples were analyzed across 16 articles and 22 independent datasets. The study showed an increased risk of allergic rhinitis in offspring as a result of tobacco exposure during pregnancy of at least 13%. Maternal passive smoking during the pregnancy period recorded the highest risk of 39%. Other epidemiological studies have shown that adverse effects from smoke-induced environmental exposures develop around the time of delivery and are strongly associated with the development of asthma or allergic diseases in the newborns. Other clinical studies showed further smoke association with lower birth weight of the newborns, which in turn may be associated with increased risk of asthma or impaired lung function.

Conclusion

According to the published meta-analysis, tobacco exposure throughout the gestational period may significantly increase the risk of allergic rhinitis in the newborns due to several factors. The researchers recommend reducing smoking during the period before the child is born to minimize genetic risk factors. Furthermore, studies exist showing that parental allergy alone could generically increase the risk of allergic rhinitis in offspring. In the absence of studies on this - whether there is an association between tobacco exposure during pregnancy together with parental allergy and allergic rhinitis in the child - analyses are still needed to clarify a definite association between the allergic and epigenetic effects of smoking.