Allergy is a reaction of our immune system response against any allergen.
Our natural defense mechanism starts producing antibodies (IgE) against invaders.
The overreaction of our immune system is resulting allergic reactions.
Any foreign substance that triggers the immune system to overreact is termed an allergen.
The immune system of the susceptible individual has mistakenly produced antibodies against the entrance of these harmless or least harmful substances by considering them as dangerous invaders.
The attack of these foreign substances is referred to as allergens, and the symptoms are termed as an allergic reaction.
The list of allergens is specific for allergic patients.
But most common allergens are pollen, dust mites, mold, spores of molds, cockroaches, animal dander, latex, etc.
Some food items like milk, nuts (peanuts), and eggs are very common food allergens.
Some individuals also have medications like penicillin allergy.
Some common allergic disorders are hay fever or allergic rhinitis, eczema and allergic dermatitis, contact dermatitis, urticaria, asthma, and food allergy.
Allergic diseases can also be classified depending upon the nature of the allergen, the affected body part, or symptoms like a food allergy.
For example, food allergy is an allergen-dependent allergy. Whereas allergic rhinitis occurs with a runny nose, asthma occurs due to allergen attacking the lung.
Impact of allergy on cancer
The different hypotheses that tried to link up between IgE-mediated allergies and cancer occurrences are conflicting.
Some of the hypotheses reported the protective role of allergies against cancer whereas others indicate triggering cancer incidences.
The first hypothesis stated that allergic reaction prevents cancer through immunosurveillance. Immunocompetent cells are overstimulated during allergy.
The overstimulation of immune-competent cells activates IgE antibody production that may have a cytotoxic influence on cancer cells.
The second hypothesis is contradictory to the first hypothesis.
According to the second hypothesis chronic inflammation due to prolonged stimulation of the immunological system in allergic conditions can lead to a chronic infection that may induce reactive oxygen species (ROS) production and may trigger oncogenesis.
Another hypothesis suggested a prophylactic effect. An allergic reaction may neutralize the mutagenic initiates before transforming malignancy in a particular tissue or cells.
Thus, cancerous growth can be prevented.
However, the final hypothesis suggested that allergic reactions may trigger inappropriate T-helper 2 immune skewing.
Individuals with any type of allergic disorder have a decreased tendency to develop cancer compare with a healthy population.
Colorectal cancer, larynx cancer, glioma, non-Hodgkin lymphoma, esophagus cancer, pancreatic cancer, oral cancer, stomach cancer, and uterine cancer are some organ-specific cancers that usually do not progress in people with allergies.
However, bladder cancer, prostate cancer, myeloma, and lymphoma risk increased with an existing history of allergies.
Here it is necessary to mention that certain cancers like breast cancer, leukemia, lung cancer, melanoma, and thyroid cancer may or may not have a link with allergy, as study findings reported conflicting results.
Further research requires for knowing the relation between allergies and liver cancer, ovarian cancer, and Kaposi sarcoma.
Impact of cancer on allergy
It is also necessary to mention that a clinical trial finding suggested that cancer patients had minimum risk to develop an allergy.
This research reported that cancer patients had significantly fewer IgE-mediated allergic diseases including allergic rhinitis, atopic dermatitis, and bronchial asthma compared with the control group.
Moreover, no significant correlations between the type of cancer diagnosed and the form of allergy.