He broke out in hives. Anywhere that he'd touched the peanut butter - his fingers, the inside of his hands, around his mouth - turned deep pink and sprouted dozens of white bumps, no bigger than the head of a pin. People frequently ask me how I knew my son was allergic to peanuts. Simple. At 10 months old, I gave him peanut butter, and he broke out in hives. Two months later at his 1-year well child appointment, I mentioned the episode to his doctor. The hives combined with ongoing eczema earned us a referral to a pediatric allergist. At that appointment, they covered his back with needle sticks laced with common allergens - peanuts, wheat, milk, eggs, soy, pollen, animal dander, mold, dust, and more. It was a grueling 20 minute wait while he sobbed and wailed but we couldn't put our arms around him for fear of cross-contaminating the samples. Growing welts confirmed what we already knew: he had spring and fall environmental allergies, and he was allergic to peanuts.