(i) Anti-histamines: It is the group of drugs which counteract the effect of histamine in the body. These are also called anti-allergic drugs. Allergic reactions are caused due to liberation histamine in the body that is why these drugs are called antihistamines. These are used to treat allergy e.g., skin rashes, conjunctivitis and rhinitis (inflammation of nasal mucosa). Commonly drugs of this group are diphenyl hydramine, chloropheni-ramine, promethazine etc. Some other commonly used antihistamines are: trimeton and benadryl etc.

(ii) Disinfectants: Disinfectants kill microorganisms, but are not safe for living tissues. These are applied to inanimate objects such as floors, drainage systems, instruments etc. Example: one percent solution of phenol, chlorine in a concentration of 0.2 to 0.4 parts per million etc.

(iii) Antacids: Substances which remove the excess acid and raise the pH to an appropriate level in the stomach are called antacids. Magnesium hydroxide, magnesium carbonate, magnesium trisilicate, aluminium hydroxide gel, sodium bicarbonate and aluminium phosphate are commonly used as antacid.