The World Health Organisation Allergen database has entries for two types of melons, watermelons and muskmelons. Muskmelons include most other melons including cantaloupe and honeydew.
Watermelons contain profilin proteins and muskmelons contain profilins as well as PR-1 proteins which are linked to Pollen Food Allergy Syndrome.
I have put together some more comprehensive resources at http://www.allergyresources.co.uk/Melon.php
The allergy resources page for melon covers the key allergens, which allergic syndromes are linked to this allergy and other foods which are commonly cross reactive with melon.
There is also regularly updated links to useful websites specifically for melon allergies and the latest research papers on the topic.
If you have multiple allergies and are interested in how they are linked or want to find out more about food allergies outside the usual top 14 then you can follow me on Facebook or Twitter, where I share a food allergy card every day of the week.