My son aged 13 loves shellfish but said he thought mussels no longer agreed with him. Last night we went out for dinner he had a huge dish of tiger prawns. I noticed his lips were bright red but thought nothing of it. Then he said can we go home. Before I paid the bill he shot off. Hubby found him in the loo, he had to go again before we could leave. Five minute drive home and he was back in the loo. He had an awful upset stomach. He then went to bed and slept. Could he be allergic to shellfish?