Summary
Overreaction of the immune system to harmless substances like pollen or peanuts.
In depth
Sensitisation: allergen exposure produces IgE bound to mast cells. On re-exposure, cross-linking triggers release of histamine, causing sneezing, hives or anaphylaxis. Treatments: antihistamines, adrenaline (epinephrine) auto-injectors, and immunotherapy.
Atopic people make more IgE. Early life exposures may influence risk (hygiene hypothesis). Mast cell degranulation releases histamine, leukotrienes and others.
Example: oral immunotherapy gradually desensitises people to peanuts.
Atopy is the genetic tendency to produce IgE against environmental allergens. Th2 cells and cytokines IL-4, IL-5 and IL-13 drive class switching and eosinophils. Common allergens include pollen, dust mites, pet dander, foods (peanuts, milk, eggs, shellfish) and venoms. Anaphylaxis is a life-threatening systemic reaction needing adrenaline (an autoinjector).
The hygiene hypothesis suggests that reduced early microbial exposure raises allergy risk, supported by lower rates in farm children. Early peanut introduction lowers peanut allergy risk (LEAP trial). Treatments include antihistamines, steroids, allergen immunotherapy and anti-IgE antibodies (omalizumab).
Example: hay fever occurs when pollen on the nasal lining triggers mast cells.
Frequently asked questions
What is Allergies?
Overreaction of the immune system to harmless substances like pollen or peanuts.
Which area of biology covers Allergies, and how advanced is it?
Allergies is one of the 52 topics in Immunology & Disease. It is rated Beginner, so it suits learners who are starting out in biology. Related topics in this area include Autoimmune Disease, Hypersensitivity Types, Immune System.
Can you give an example of Allergies?
Peanut allergy can cause life-threatening anaphylaxis.
What should I learn before Allergies?
Allergies is a Beginner topic, so no earlier topic is required. Other Beginner topics in Immunology & Disease that pair well with it include Immune System, Viruses, Innate Immunity.
What topics are related to Allergies?
The closest topics to Allergies are Autoimmune Disease, Hypersensitivity Types, Immune System, Primary and Secondary Response. Comparing them side by side is a good way to see how the ideas connect.
How can I check that I understand Allergies?
Read the summary and the in-depth section, then use the quick check on the interactive lesson for Allergies. To practise the whole of Immunology & Disease, use the Immunology & Disease quiz.
How is Allergies different from Autoimmune Disease?
Allergies: Overreaction of the immune system to harmless substances like pollen or peanuts. Autoimmune Disease: The immune system attacks the body's own tissues, as in type 1 diabetes and rheumatoid arthritis. Read both side by side and note what each one explains.
How should I study Allergies step by step?
First, read the summary and write the definition in your own words. Second, read the in-depth section and note any example. Third, compare it with Autoimmune Disease and explain the difference aloud. Finally, take the Immunology & Disease quiz and come back to this page for any question you miss.