Is it true your body makes changes, say allergies, menstrual cycle (associated symptoms etc) and or developments at certain ages?

Yes: We call it the allergic march. I prefer the allergic marathon. Eczema tends to be 1st followed by asthma (which has a bimodal occurrence) followed lastly by onset of allergy symptoms. None of this is set in stone. And most definitely, hormonal fluctuations wreak havoc on allergy symptoms.

Hormones and allergy: It is pretty common to see woman develop sino- nasal symptoms when they go on or off hrt, go through pregnancy or start getting their menses. Additionally we often time see chronic urticaria in patients with positive antithyroid antibodies-ie- hashimoto's thyroiditis.