Nitroglycerine is usually given as a tablet dissolved under the tongue. The tongue has a rich vascular supply that allows the nitroglycerine to get into the blood stream about as fast as an intravenous injection. That is why allergy drops given under the tongue work as well for most people as allergy injections under the skin. Some people, however, still prefer the injection form thinking that they can be more certain about the amount that they receive. Drops have the advantage of not having to use needles. The disadvantage is that drops must be given daily whereas the injections are usually given once a week for inhalants and twice a week for foods. If sunlight and heat are avoided, drops may not require refrigeration but injectables will require refrigeration. For the chemically sensitive, drops may be carried about and used when an overwhelming exposure occurs.
Treatment can be by either intradermal or sublingual. The patient chooses. Some patients try one and then the other. Intradermal treatment is for once or twice a week, depending on the antigen. Sublingual is daily but no syringes are required.