Breast allergic condition was associated with a low risk

Breast cancer (BC) is the second cause of cancer
related mortality among women worldwide. In 1985, a large study reported no
association between BC risk and hay fever, but the risk of BC was rather decreased
in women with history of hives or other allergies (20). In another
study among Canadian women, a history of allergies or hay fever was related
with a low risk of BC (OR = 0.86, 95 % (CI): 0.77–0.96) (31). Also, among young
American women, an allergic condition was associated with a low risk of BC (32). In a linkage
study, contact allergy has been associated with decreased BC risk (33). Other several
studies of allergies and BC risk reported no association, although may not have
had enough power to evaluate this association (34-36). Case control studies evaluating relationships
of allergy and breast cancers was shown in table1.

In Canadian individuals, asthma was not related with
BC risk overall; but, a significant decrement in BC risk was observed only in
premenopausal women (31). The reason may
be explained by difference in pattern of asthma among pre- and postmenopausal women,
as allergic asthma is usually occur earlier compared to non-allergic asthma (37,
38) which affects
older people (39-42).

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Pancreatic cancer (PC) as
a fourth cause of cancer related mortality worldwide has extremely poor
prognosis. A meta-analysis of 14 PC studies showed the 30% and 45% lower risk
in subjects with history of any allergies and nasal allergies, respectively (43). Also, several studies have confirmed their
finding, but only one study estimated
a non-significant decreased risk.

Other review exploring 11 published studies reported
reduced risk of PC in respiratory allergy conditions such as allergies to
plants or pollen or hay fever (48). Regarding skin
allergies, two studies announced negative association but only one reached
statistical significance(46,
47).

In a study conducted on 1297 PDAC cases and 1024
normal controls revealed that asthma was related with reduced risk of PDAC
(OR=0.64, 95% (CI):0.47-0.88) which consist with a result of meta-analysis of
10 case–control studies (OR=0.73, 95% CI 0.59- 0.89). Nasal allergies and associated
symptoms were protective factor for PDAC (OR=0.66, 95% CI: 0.52-0.83 and OR=
0.59, 95% CI: 0.46-0.77, respectively) which confirmed by a meta-analysis of
nasal allergy studies (OR=0.6, 95% (CI):0.5- 0.72) (49).

Controversy, cohort studies among Sweden(50,
51) and United States
(36) population reported
no association between PC risk and serum Ig E levels, history of Allergy, or skin
prick tests. These inconclusive results may be attributed to young studied population
and short follow up, resulting to only a small number of cases; Furthermore,
data were not adjust for potentially confounding factors.

The underlying mechanisms of association between Allergy
and PDAC risk are unclear. It has been proposed that hyperactive immune system
involved in subjects with Allergy(10). Furthermore,
susceptibility and severity of asthma and allergies are known to be affected by
genetic factors and interactions between gene and environment(52,
53). A recent study
exploring SNP in 56 allergy-related candidate genes demonstrated that specific
genetic variants may be related with a fewer PC risk (54). Further
researches are needed to clarify the role of genetics in these relationships. Bedside,
it has been found that cromolyn as an anti-allergic agent can suppress
proliferation and propagation of human PC cells invitro and invivo (55).

Colorectal cancer (CRC) is another most common malignancies
regarding to incidence and mortality (56).  Studies reporting the association of Allergy
and digestive tract tumors have had different results (10).
Allergy
were described to be protective factors in a case–control study on 715 CRC patients
in Australia (57). Another case–control
study including 1078 cases and 1501 controls demonstrated that drug allergy was
linked with the reduced risk of colon cancer (OR=0.6; 95% CI: 0.4–0.9) and
rectum tumors (OR=0.6; 95% CI: 0.4–1.0). Consistently, another hospital-based
study in Italy among 1225 colon cancer patients, 728 rectum cancer patients and
4154 well-matched controls also proposed a protective role of Allergy for CRC(58). Although, this
study used self-reported history of atopy and did not differ between various
types of allergies; so, it may be lead to misclassification. In contrast,
cohort studies did not approve the protective effect of atopy against CRC. A
prospective data analysis of first National Health and Nutrition Examination
Survey (NHANES I) showed RR of 1.7 (95% CI: 0.9 to 3.1) among 45 CRC patients
regarding to any type of allergy(36). Another cohort
study in California reported (RR=1; 95% CI: 0.7–1.3) for colon cancer and (RR=0.9;
95% CI: 0.5–1.4) for rectum cancer (59). The cohort
study noted that Allergy was a protective factor, although non-significant for
CRC (35). Cohort
studies investigating association between AAC and colorectal cancers was
presented in table2.

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