Atopic dermatitis and the 'hygiene hypothesis': too clean to be true?

Abstract

Although population-based studies have suggested a consistent inverse relationship between AD and increasing family size, this does not seem to be explained by a straightforward increased exposure to a single environmental pathogen. The effect seen with early day care, endotoxin and animal exposure may be due to a nonpathogenic microbial stimulus of a chronic or recurrent nature. This would also explain the risk increase associated with antibiotic use. Caution should prevail in the prescribing of antibiotics early in life, especially in children with a family history of AD. Larger well-designed pragmatic trials on probiotics and the prevention and treatment of AD are now needed to inform whether such interventions should be used in routine clinical practice.

Potential risk factors of food allergy in children: EuroPrevall project results in Vilnius, Lithuania

“…It is known that in recent decades there was a significant increase in the use of antibiotics to treat children's upper respiratory tract infections. Many authors consider that antibiotics cause changes in intestinal microflora, thus creating favourable conditions to prevail Staphylococcus aureus and coliforms, which may contribute to allergic diseases such as asthma, atopic dermatitis or rhinoconjunctivitis, however, links to food allergy were not found [12,[26][27][28].…”

Environmental Pollutants and Pediatric Asthma

“…future science group future science group explained by a straightforward increased exposure to a single environmental pathogen [11]. The effect found with early day care, exposure to animals and endotoxins may be due to a nonpathogenic microbial stimulus of a chronic or recurrent nature.…”

Aetiopathogenesis of atopic dermatitis

“…[17,19] The following factors have not been inconclusively shown to affect the risk for/prevalence of AD:…”

“…• rural compared with urban living (hygiene hypothesis) [13,14,17,18] • maternal AD history (parent-of-origin effect) [10,18,19] • higher socioeconomic status [12,14,20] • higher educational level of parents [21] • smaller family size (hygiene hypothesis) [17,22] • improved basic hygiene (hygiene hypothesis) [17] • antibiotic use early in life (hygiene hypothesis) [17,21] • caesarean section delivery [23] • increased maternal age [19] • environmental tobacco smoke (major risk) [13] • contact dermatitis [24,25] • cooler climates [13] • clothing with rough fibres [26] • environmental pollution [13,17] • psychosocial stress. [21,23] The following factors have been shown to decrease the risk for/ prevalence of AD:…”

“…• day-care attendance [17] • animal exposure early in life (hygiene hypothesis) [17,21,23] • endotoxin exposure in early infancy (hygiene hypothesis) [17] • infections early in life (hygiene hypothesis) [17] • breastfeeding [19,27,28] • fully hydrolysed formula feeds [21,27,28] • vaccination (hygiene hypothesis). [17,19] The following factors have not been inconclusively shown to affect the risk for/prevalence of AD:…”