Definition: A disorder of the immune system causing adverse reactions to substances (allergens) not harmful to most and marked by the body's production of histamines and associated with atopy, anaphylaxis, and asthma.

Alright class, settle down now, let’s take a look! Today we’re diving into a word that can cause a bit of woe – “allergy.” The dictionary gives us a pretty detailed definition, so let's break it down nice and slow. Essentially, an allergy is like this: it’s a problem with your body’s defense team. You see, usually, your immune system is fantastic at protecting you from germs and things that could make you sick. But sometimes, it gets a little confused! Let's unpack those words – “allergens.” Think of allergens as sneaky little troublemakers - like pollen from flowers, peanuts, or maybe even certain types of dust mites. Most people aren’t bothered by them, they just pass right through. But you , with an allergy, your system sees them as a threat! Because of this reaction, your body starts to make something called “histamines.” Histamines are like little messengers that cause all sorts of symptoms – itchy skin, runny nose, watery eyes... it can be quite a show! And we’ve got some bigger words here too: "atopy," which refers to a tendency towards allergic conditions; "anaphylaxis" - a very serious reaction that needs immediate medical attention (like a sudden drop in blood pressure); and “asthma,” where allergies can trigger breathing problems. So, remember this rhyme: An allergy's a misfire, a mistake you see, Your immune system reacts, for you and for me! Do you have any questions about what we’ve just discussed? Let's talk it over – don’t be shy!