Food allergies can be life threatening because of the bodies reaction to the food that is either ingested, sometimes touched, sometimes inhaled. The bodies reaction is to save itself. What can happen is that a person, not just a child, can have hives,can be on one local area, can be all over. But also it can start to break down some of your body parts. So that means it can enlarge your tongue to block your airway. You can have what happens with my daughter when she has had a severe reaction is she starts to cough. She also has the excema. She also has asthma. So that increases the likelihood that if she has a bad reaction it is going to get bad fast. It is life threatening because if you can't breathe because of the allergic reaction blocking your airway then you could die.