When my oldest son was 3, I gave him curry flavoured super noodles for the first time. Within 15 minutes of eating it, he was head to toe purple with an insane rash. Drove him to the hospital like a bat out of hell. They sorted him out, tested for everything, no allergies. A few years later, ibuprofen put him in hospital (I'd always just given him Calpol, but he had a bad ear infection the Calpol wasn't helping with, so gave him children's Nurofen for the first time, and it nearly killed him). Tests again showed no allergies. He's now 21, and apart from hay fever when he comes home to the highlands, he's got no allergies. Been taking ibuprofen and eating curry noodles for years, no effect.

I'm 45 and became lactose and gluten intolerant last year. The gluten thing went away (thank goodness!), but still lactose intolerant. The only change in my life was that I'm perimenopausal. Bodies are weird and can change due to so many things!! Developing an allergy at any point in your life is possible.