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Does avoidance of peanuts in early life reduce the risk of peanut allergy?

BMJ 2010; 340 doi: https://doi.org/10.1136/bmj.c424 (Published 11 March 2010) Cite this as: BMJ 2010;340:c424

Rapid Response:

Peanut allergy: the importance of environmental exposure

We read the interesting article by McLean and Sheikh about the
uncertainties
regarding the avoidance versus the early introduction of peanuts in the
diet
of children in order to reduce their risk of peanut allergy.

We feel that another important point should be added to the
discussion, that
is the role of other routes of sensitization in the development of peanut
allergy. In fact a theoretical model of allergy sensitization proposes
that the
different routes of entrance of antigens can influence the development of
tolerance. The gastrointestinal mucosal immune system is constantly facing

an enormous quantity of antigens (food and physiologic gut microbial
flora)
and must therefore suppress its reactivity and develop tolerance [1]. The
mechanisms are still not fully understood but certainly include antigen
presenting cells and regulatory T cells. Intestinal cells can process
antigens
and present them to T cells without the presence of a second signal, thus
leading to anergy. On the other end entrance of an antigen through the
skin
generally represents a pathologic situation.
Loss-of-function variants of the epidermal barrier protein filaggrin have
been shown to predispose to atopic dermatitis and asthma [2]. Application
of
food antigens to the skin of mice can lead to the development of systemic
allergy after food ingestion [3]. This is particularly true when there is
loss of
skin barrier.

Most importantly an epidemiological study has shown that high levels
of
environmental exposure to peanut during infancy, rather than children or
maternal consumption, appears to promote sensitization [4]. Another study
found a correlation between peanut allergy and history of application of
peanut oil to inflamed skin [5].
Therefore presentation of antigens through the skin or the respiratory
tract
rather than, or maybe in the absence of, oral exposure might preclude the
development of tolerance.

Considering these data, although many uncertainties still exist, the
importance of environmental exposure should be taken into consideration
when giving advice to patients and their families. The article by du Toit
et al.
[6], cited by the authors as well, seems to suggest that oral avoidance is
not
useful, even though further studies are needed. In fact it may be
difficult to
completely avoid environmental exposure and the contemporary absence of
oral exposure could impair the development of tolerance. Nevertheless
further studies are needed to demonstrate these ideas.

References.

[1] Sicherer SH, Sampson HA. Food allergy. J Allergy Clin Immunol
2010;125:S116-25.

[2] Palmer CN, Irvine AD et al. Common loss-of-function variants of
the
epidermal barrier protein filaggrin are a major predisposing factor for
atopic
dermatitis. Nat Genet. 2006 Apr;38(4):441-6.

[3] Strid J, Thomson M, Hourihane J, Kimber I, Strobel S. A novel
model of
sensitization and oral tolerance to peanut protein. Immunology
2004;113:293-303.

[4] Fox AT, Sasieni P, du Toit G, Syed H, Lack G. Household peanut
consumption as a risk factor for the development of peanut allergy. J
Allergy
Clin Immunol 2009 Feb;123(2):417-23.

[5] Lack G, Fox D, Northstone K, Golding J. Factors associated with
the
development of peanut allergy in childhood. N Engl J Med.
2003;348(11):977–985.

[6] Du Toit G, Katz Y, Sasieni P, Mesher D, Maleki S, Fisher H, et
al. Early
consumption of peanuts in infancy is associated with a low prevalence of
peanut allergy. J Allergy Clin Immunol 2008;122:984-91

Competing interests:
None declared

Competing interests: No competing interests

13 March 2010
Samuele Naviglio
junior doctor
Fabrizio Pirozzi
University of Trieste, Italy, 34100