White blood cells produce antibodies to target allergens
Our bodies are constantly reacting to their surroundings. When it gets cold, your muscles work to warm you up. When you need food your stomach rumbles to alert you. When bacteria or viruses enter your body, cells instantly recognise them as harmful intruders to target.
The latter is performed by your immune system, a preprogrammed defence system consisting of organs, cells and proteins that is active throughout your entire body. As well as detecting threats to physical health, the immune system can sometimes become overactive, triggering an unnecessary response to non-toxic substances. This is how allergic reactions arise.