Q. I have three children, aged 12, 7 and 18 months. My 12-year-old daughter developed peanut allergy at 2. My 7-year-old daughter had a test at 3 and wasn’t allergic to peanut. Now at age 7, she is. Why is that? And is there anything preventative I can do for my 18-month-old son? Dr. Watson: [...]