A new meta-analysis suggests that allergies do not broadly protect against cancer, and that asthma and regional differences form small but important risk signals.
Research: Association between allergies and cancer incidence: A systematic review and meta-analysis. Image credit: Belhadef.nabil / Shutterstock
In a recent press research article published in the journal scientific reporta group of researchers used cohort-based evidence from multiple countries to assess the association between allergic disease and subsequent cancer development.
Can a condition as common as allergies influence the likelihood of developing cancer?While an estimated 10% to 30% of the world’s population experiences allergic diseases, cancer remains a leading cause of suffering and death in both men and women.
There has been much debate among scientists about whether allergies actually help the body’s immune system recognize and eliminate cancer cells, or whether long-standing allergic inflammation increases the risk of developing cancer. Different allergic conditions trigger different immune responses, further complicating this relationship.
Understanding how allergies and cancer are related has the potential to improve public health strategies and guide future research.
About research
The researchers conducted a systematic review according to the International Prospective Register of Systematic Reviews (PROSPERO) protocol (registration number CRD42024566792). To identify eligible studies, a search of cohorts published between 1999 and 2024 was performed using PubMed. To ensure that no relevant evidence was missed, the researchers checked the reference lists of the selected articles using Google Scholar and Scientific Electronic Library Online (SciELO).
The study also included patients who were diagnosed with allergies before developing cancer, confirming that the allergic disease was present before the cancer diagnosis. Studies involving acute allergic reactions, special patient populations, and studies without a cohort design were excluded. Both solid tumors and hematologic cancers were considered as outcomes.
Researchers extracted study characteristics including country, study design, participant demographics, sample size, allergy type, cancer type, effect estimate, and 95% confidence interval (CI). The Newcastle-Ottawa Scale (NOS) was used to assess study quality and Rayyan was used to screen the literature.
Meta-analysis was performed using Stata 18.0 statistical software with random effects model. Effect estimates such as odds ratios (ORs), hazard ratios (HRs), relative risks (RRs), and standardized incidence rates (SIRs) were converted to logarithmic scales, and HRs, RRs, and SIRs were treated as approximations of ORs under the rare outcome assumption before statistical analysis. Subgroup analyzes examined differences by geographic region, allergy type, and cancer type, and assessed heterogeneity and publication bias using I2 statistics and Egger tests.
Research results
This systematic review included 28 eligible studies conducted in the United States, Sweden, Taiwan, United Kingdom, Denmark, Australia, Finland, and South Korea. Most were cohort studies and included two nested case-control studies that met predefined eligibility criteria.
The study evaluated a wide range of allergic conditions, including asthma, hay fever, atopic dermatitis, and atopic allergy conditions, as well as multiple types of cancer that affect different organs and tissues.
All included studies were rated as moderate or high quality using NOS, but the pooled evidence required cautious interpretation due to substantial heterogeneity, potential publication bias, and subgroup limitations.
A primary meta-analysis showed an overall weak but statistically significant association between allergic diseases and cancer incidence. The combined OR for individuals with allergic disease and cancer incidence was 1.07 (95% CI: 1.03-1.11), indicating that having an allergic disease was associated with a small increase in overall cancer risk. Although the effect size was limited, the findings suggested that allergies do not consistently protect against cancer across the study population.
Inspection of funnel plots revealed visual asymmetries, and Egger tests did not identify statistically significant small study effects, suggesting that publication bias cannot be completely ruled out.
Allergies were statistically associated with cancer incidence in the Western Pacific region (OR 1.65, CI: 1.22-2.21), but there was no statistically significant association between allergies and cancer in the Americas or Europe. Although these regional differences suggest that the allergy-cancer relationship may vary by population or geographic setting, the Western Pacific subgroup is based on a limited number of studies and may reflect differences in population, environment, or cancer type.
Additional subgroup analyzes of cancer types found an association between allergies and the incidence of the following cancers: lung cancer, blood cancer, kidney cancer, testicular cancer, and thyroid cancer. However, colorectal cancer and uterine cancer showed an inverse association (negative association) with allergy.
Several other cancer types were also evaluated, including breast, ovarian, prostate, skin, cervical, liver, endocrine, and upper aerodigestive tract cancers, but not all showed statistically significant associations. Additionally, many of the type-specific analyzes were small. Therefore, the findings should be interpreted with caution.
When only type of allergy was considered, only asthma had a statistically significant association with cancer incidence (OR 1.18, 95% CI: 1.10-1.28). On the other hand, atopic dermatitis, hay fever, and atopic diseases showed no statistically significant association.
However, the authors pointed out that asthma signals may partly reflect not only the pathophysiology of the allergy but also the severity of the allergy and treatment-related confounds, particularly the use of corticosteroids.
This analysis also showed heterogeneity across studies due to different study populations and different definitions of allergy and cancer outcomes.
Our findings therefore suggest that the relationship between allergy and cancer is complex and varies by allergy type and geographic region, with no consistent pattern across regions, allergy subtypes, and cancer outcomes.
conclusion
The results showed a statistically significant but modest association between allergic disease and overall cancer incidence. Although the overall increase in risk was small, important differences emerged by geographic region and allergy type, with the strongest association observed in the Western Pacific region and among people with asthma.
The variability in results across cancer-specific assessments, and the limited number of studies in several subgroups, highlighted the need for further research to identify subgroups at increased risk and better define the allergy-cancer relationship, rather than prompting immediate changes in current clinical practice.
Reference magazines:
- Ishiguro, H., Palvin, R., Hirabayashi, M., Inoue, M., and Abe, S. K. (2026). Association between allergies and cancer incidence: A systematic review and meta-analysis. scientific report. Doi: 10.1038/s41598-026-56988-3, https://www.nature.com/articles/s41598-026-56988-3
