Why doesn't mangoes have a warning label? i know 2 friends with mango allergy.

Mangos are a Fruit: Allergy warning labels are not typically placed on fruit.

Uncommon allergy: The Food Allergen Labeling and Consumer Protection Act (FALCPA), which took effect January 1, 2006, mandates that the labels of foods containing major food allergens (milk, eggs, fish, crustacean shellfish, peanuts, tree nuts, wheat and soy) declare the allergen in plain language. These 8 food make up about 90% of all food allergies. The other 10% includes many other foods including mango.