Dr. Nashed has a special interest in the relation between Allergy and Cancer.
     He did 2 studies about the relation between the long term use of allergy medications for over a year and the risk of cancer.
Published Abstracts

1. Daily use of allergy/asthma medications for more than one year might be helpful to decrease cancer prevalence

The background of the study:
Recurrent or persistent inflammation may influence susceptibility to carcinogenesis by causing inciting tissue reparative proliferation, and/or creating a stromal "soil" that is enriched with cytokines.
TH2 cells orchestrate the asthmatic/allergic inflammation through the secretion of a series of cytokines, particularly interleukins 4(IL-4), IL-13, IL-5, and IL-9. IgE (regulated by IL4) bound to mast cells triggers histamine release, prostaglandins and Leukotrienes synthesis, and cytokines transcription. IL-4 and IgE induce nitric oxide synthase (iNOS) in human macrophages. Administration of iNOS inhibitor limit invasion and growth rate of iNOS transfected tumors. Inhibitors of IL-13 may prove useful in the treatment of some cancers like B-cell chronic lymphocytic leukemia and Hodgkin's disease, where IL-13 modulates apoptosis or tumor cell growth.
Do Antihistamines, Inhaled Steroids, Leukotrienes Antagonists, and Oral Steroids, which block these mediators’ effects, have also an effect on cancer?

The method used: 8000 survey papers were placed at 24 physician offices. Patients were questioned if they have/ had allergy ± asthma, cancer, or both. They were also asked what medicines they used, and for how long. Patients were disqualified if they did not mention if they had cancer or allergy ± asthma.

The results obtained: 710 surveys were completed. 363 did not have allergies or asthma (34 had cancer -9.37%). 333 had allergies ± asthma (45 had cancer-13.51%)[207 used no medicine or used medicines on demand or used them regularly for less than a year (32  had cancer -15.46%)].126 used one medicine or a combination of medicines daily for over one year (13  had cancer -10.31%), 87 of the126 took antihistamines either alone or in combination (7 had cancer -8.05%)]. 14 were disqualified. There was a decrease in the percentage of cancer patients from 15.46% to 10.31% (or 8.05% in the subgroup-P value 0.055) when allergy medications were used daily for over one year. The results do not have statistical significance because of the number of responders, but could have great clinical significance if confirmed.

The conclusion reached: This survey may suggest that using daily allergy medications for over one year might help decrease cancer prevalence. Since allergy medicines have been well tolerated without significant long-term side effects, studying their effects on cancer - either separate or in combination- might be worth further investigations.

2. Can Antihistamines Decrease Cancer Risk If Used Daily For Over One Year?

Rationale: Epidemiologic studies have found inverse associations between allergy and the development of certain tumors. Allergy treatment has not been looked at as a factor of this association.

Methods: A survey was conducted on patients of 7 allergists’ offices. Patients were divided into 2 groups. In one group, the survey questionnaires were answered from the medical records by the nurses and patients’ responses if available (1539 patients). The second group voluntarily answered the survey (521 patients). The survey lasted for 2 months, ending in May 2007. Patients were excluded if their allergy symptoms were < 1 year or < 18 years old, or if had cancer before their allergy symptoms began.  Medications used, their duration, if used daily (80 to 100% of the year) for over a year were requested. The study was approved by Essex Institutional Review Board.

Results: The risk of developing cancer in the first group was 1.93% for daily antihistamines and 4.76% for as needed medications and with P value 0.0081. In second group the risk of cancer was 5.31% for daily medications and 6.84% for as needed group. The difference was not statistical significant.

Conclusion: Daily intake of antihistamines, when well documented, for > 1year may be associated with decrease cancer risk. Repeating the same work on a larger scale by others might be needed before confirming this association.