Two-year-old Ruben Curie has such a severe allergy to tomatoes that even touching a dollop of tomato ketchup could kill him.
His allergy is so severe that the slightest contact with the sauce could send him into a potentially fatal shock.
Ruben has to avoid the ketchup to stay alive - even though the rest of his family regularly have it on their tea.
His mother Kasi, 24, says her son is lucky to be alive after being rushed to hospital when tomato ketchup touched his finger.
Ruben was rushed to the Royal Glamorgan Hospital to be given steroid injections - and within 15 minutes the swelling from anaphylactic had subsided.
Mrs Curie said she first realised something was wrong with Ruben when he was six weeks old. He was covered in angry, red marks that looked like burns.
His mum said: "I realised he must be allergic to something so I kept a food diary. A pattern emerged when he ate anything with tomato in it."
The family, who live in Rhondda, rarely eat out because they fear cross-contamination.
She said: "Even prawn cocktail crisps are a problem because they have tomato powder in them. We can't risk eating out very often because we don't know exactly what is in the food."
Doctors told the family having a sensitivity to tomatoes in very common but having a anaphylactic reaction to them is very rare.
Mrs Curie said she is now waiting for Ruben to see an allergy specialist.