Although many people believe they are allergic to chocolate, true allergies to chocolate – specifically, the cocoa it's made from – are actually rare. In addition, many reactions to chocolate are not true allergies to the chocolate itself, but are rather allergies or intolerances to other ingredients in the chocolate, such as milk, nuts, gluten, corn syrup, dyes, or other additives. Alternately, people may be sensitive to the naturally-occurring chemicals in chocolate. These include caffeine, theobromine, and phnylethylamine.
Whatever the case may be, common reactions to chocolate in those who are affected include headache, heartburn, skin rashes, and breathing problems. Sensitivity to chocolate ingredients can also trigger asthma attacks.
One reason for the prevalence of reactions to chocolate is that a good part of mainstream chocolate products in the United States contain several additives; it's these that people react to. The purest forms of chocolate contain cocoa liquor, cocoa butter, sugar, maybe vanilla – and nothing else. Mass produced chocolate, on the other hand, is often primarily composed of the additives mentioned above (milk, corn syrup, dyes, etc.).
If an allergist has diagnosed you with an actual cocoa allergy, of course you need to stay away from it altogether. In addition, if you have an allergy to milk, nuts, or corn, don't take any chances eating chocolate. (For more on food allergies, see the Food Allergy FAQ.)
However, if you are intolerant of ingredients that may be included in inexpensive chocolate varieties, try a premium quality chocolate that comes closer to chocolate's purer form. One of my all-time favorites is Chocolove. Mmmmmm….