Basically there are three major types of kosher foods. They are categorized according to their contents as kosher meat, kosher dairy and kosher parve. There are strict guidelines on how they are prepared which is defined in the kashrut guidelines. For instance, meat and dairy to be kosher must not be prepared together nor be served on the table at the same time. The Torah teachings provide that the mother and its milk cannot be served and eaten together thus this prohibition under the kashrut guidelines.
Kosher meats to become kosher are properly selected based on the characteristics that are defined by the Jews dietary law. The animal is chosen based of having a cloven hooves and chews its cuds. Animals that do not meet this characteristic are not fit to be kosher. Fowls are generally recognized kosher meat so are chickens, hens, turkeys, geese, duck and other domesticated animals. There are however certain fowls that are identified by the Torah as forbidden animals like scavenger birds and predators. To make an animal meat kosher, it is also essential that the meat source should come from an animal that did not suffer from pain when slaughtered otherwise even if the animal is kosher it will still render the animal non-kosher.
Kosher dairy are those that come from kosher animals and are required to be free from derivatives. They are labeled with OK or D symbol in the package to indicate that the kosher food contains milk or dairy products. If you are allergic from dairy or milk products reading the labels will help you avoid ingredients from a kosher food product that might flag a warning that it is not good for you. This makes kosher parve foods more suited to your condition as this do not contain dairy or meat products. They are neutral and they cannot cause you any adverse health reactions like an allergy. However, some kosher parve foods may contain egg and you might be allergic to it as well. Reading the labels of the ingredients contained in a kosher parve package will help you identify which food is safer for your condition.