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Allergies Basics Immune system

Allergies 101 — What's Actually Going On In Your Body

A straight-talking breakdown of how allergies work, why they can be so brutal, and what you can realistically do about them.

If you live with allergies, you already know what they feel like.

What most people never get told is what’s actually happening under the skin — and why one person can eat a peanut for fun while someone else ends up in A&E from a crumb.

This is the stripped-back version.

Allergies in one sentence

Your immune system has decided something harmless is a threat and now treats it like a full‑blown invasion every time it shows up.

That “something” could be:

  • A food protein (peanuts, tree nuts, lupin, sesame, dairy, egg, etc.)
  • Pollen
  • Dust mites, moulds
  • Insect stings
  • Certain drugs

The key word is overreaction. The thing itself isn’t poisonous. Your immune system’s response is the problem.

Step by step: what happens during an allergic reaction

  1. Sensitisation
    The first time (or early times) you meet the allergen, your immune system quietly takes notes.
    For some people, it flags it as “enemy”. You make specific IgE antibodies against it.

  2. IgE antibodies park on mast cells
    These antibodies sit on the surface of cells like mast cells and basophils, waiting. Think of them as tripwires.

  3. Next exposure: the tripwires fire
    You meet the allergen again. It binds to the IgE on those cells, cross-links them, and that’s the trigger.

  4. Chemical dump
    The mast cells degranulate and dump chemicals like histamine, leukotrienes and more into the area and bloodstream.

  5. Symptoms
    Those chemicals cause:

    • Itching
    • Hives / rash
    • Swelling
    • Stomach cramps, vomiting, diarrhoea
    • Tight chest, wheeze
    • Drop in blood pressure, dizziness, collapsing (in anaphylaxis)

Same mechanism, different severity.

Food allergy vs intolerance (and why the wording matters)

People throw these words around like they’re interchangeable. They’re not.

  • Allergy (IgE‑mediated or mixed)

    • Immune system based
    • Can involve skin, gut, lungs, circulation
    • Can be life‑threatening (anaphylaxis)
    • Often happens quickly — minutes to a couple of hours

  • Intolerance

    • Usually not driven by IgE
    • Often about digestion (e.g. lactose intolerance = not enough lactase enzyme)
    • Symptoms can be grim, but don’t trigger anaphylaxis
    • Often dose‑dependent

If there’s even a question mark over whether you’ve had breathing changes, throat tightness, sudden severe symptoms or collapse, that moves you into “take this very seriously” territory.

Tests that actually mean something

None of this replaces a proper allergy specialist, but here’s what’s normally used:

  • Skin prick testing

    • Allergen is pricked into the skin.
    • A wheal (raised bump) and redness suggests sensitisation.
    • Interpretation matters — a positive test doesn’t always equal real‑world reactions.

  • Specific IgE blood tests

    • Measures how much IgE you have to a specific allergen.
    • Again: sensitisation ≠ guaranteed reaction, but it’s part of the puzzle.

  • Component‑resolved diagnostics (CRD)

    • Looks at specific proteins within an allergen (e.g. peanut components like Ara h 2).
    • Helps separate “might tingle a bit” from “this can put you in intensive care”.

  • Oral food challenge

    • Done in hospital.
    • You’re given small, increasing amounts of the food under supervision.
    • Gold standard for confirming or ruling out a food allergy.

If a GP or random practitioner is making sweeping claims off a single test sheet without context, be wary.

Avoidance: boring, but non‑negotiable

If you’ve had serious reactions, there’s no pretty way to say this:

Your number one treatment is still avoiding the thing that tries to kill you.

That means:

  • Becoming fluent in label‑reading
  • Watching for “may contain” vs “made in a factory with” and understanding the risk tolerance that you and your specialist agree on
  • Calling restaurants and asking direct questions
  • Accepting that some places will never be worth the risk

You don’t have to like it. You do have to respect it.

Emergency plans and adrenaline

If there’s even a hint of serious allergy, you should have:

  • Adrenaline auto‑injectors (e.g. EpiPen, Jext, Emerade where available)
  • A written action plan from your allergy team
  • People around you who know:
    • Where your pens are
    • When to use them
    • That one jab doesn’t magically fix everything — you still call emergency services

If in doubt: use the pen and call for help. Waiting to see “how bad it gets” is how people die.

Where mindset fits in

You don’t need to be endlessly “positive”. You do need to be:

  • Clear‑headed about the risk
  • Ruthless with boundaries (especially with people who minimise it)
  • Honest about anxiety and burnout

Allergies are medical. The emotional fall‑out is real too. Both deserve attention.

The bottom line

Allergies aren’t “just fussy eating” or “a bit of hay fever”.

They’re the result of a smart immune system making a bad call and doubling down hard every time the trigger appears.

You’re not weak for taking it seriously. You’re staying alive.

Future posts will go deeper into:

  • Specific allergens (nuts, sesame, lupin, etc.)
  • How to push for proper testing
  • Dealing with family, friends and restaurants who “don’t believe it’s that bad”
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