The WHO Allergen Database has entries for 2 types of melons, watermelons and muskmelons.
Muskmelons have been cultivated into subtypes and include most other melons including honeydew and cantaloupe melons.
The watermelon has only 1 defined food allergen, called Citr l 1, this is a profilin protein. Reactions to watermelon are most commonly oral allergy type symptoms.
The muskmelon group of fruits contain 3 food allergens, called Cuc m 1, m 2 and m3.
Cuc m 2 is a profilin, similar to that of Citr l 1 in watermelon.
Cuc m 1 is a plant enzyme called cucumisin.
Cuc m 3 is a common plant protein called PR-1, which protects the plant from attack.
You may have Pollen-Food Allergy Syndrome if you suffer from melon allergy with oral allergy symptoms to 3 or more of the foods mentioned in cross reactivity section.
If sensitised to Ragweed pollen you may also have problems with Banana, Melon, Courgette, Cucumber, and Squash.
If sensitised to Grass pollen you may also react to Melon, Potato, Oranges and Peanuts.