Kitty "cold" is another name for upper respiratory infection. The infection's severity will warrant whether veterinary treatment is needed. Medication is probably not needed if your cat has only clear discharge from its eyes and nose and if it is eating and drinking. If the discharge becomes thick or colored or if the animal stops eating or drinking, medical support is needed.
Most of the microorganisms that cause URIs are airborne, and both indoor and outdoor cats are at risk. URIs can have incubation periods of a few days to a week. URI will respond rapidly to antibiotic treatment if the cause is bacterial. Viral infections do not respond to antibiotics and last 7 to 14 days. Just like humans, cats need to drink plenty of fluids and also rest when they have bad colds.
Getting your cat to eat when it has a URI may also be difficult. If a cat cannot smell, often it will not eat. To encourage eating, you may want to try canned food or tuna or even microwave the food slightly to improve the aroma. You can try baby food, but be sure to use meat types that do not include onion powder.
Veterinary care is needed if you cannot get your cat to eat or drink. Your veterinarian may treat your cat with fluids either intravenously or subcutaneously (under the skin). He or she may also hand-feed or force-feed your cat. Antibiotics may be given.
Congested airways and sinuses can be relieved with vaporizers or humidifiers. Cleaning the discharges that build up around the cat's nostrils will help breathing and smell. Pediatric nasal drops can be used in cats, but consult with your veterinarian about proper use of these or any other over-the-counter treatments.
Many cats with URIs will have conjunctivitis. If the discharge around the eyes is watery and clear, you can clean it with a moist tissue. If the eyes are red, inflamed and squinting, prescription medication is probably needed.
URIs are extremely contagious. In multicat households, it is almost impossible to limit infection to one cat. There are no good preventives against URIs except annual vaccination and decreasing the contact your cat has with other cats.