Catnip, also known as catmint, is a plant belonging to the mint family, which contains a chemical compound called nepetalactone. This compound is responsible for the unique and highly pleasurable reaction that many cats exhibit when exposed to catnip. However, the response to catnip varies among individual cats, and not all cats are affected by it.

It is believed that the sensitivity to catnip is an inherited trait, meaning that some cats are genetically predisposed to responding to catnip, while others are not. Studies have shown that around 70-80% of domestic cats are affected by catnip, and the sensitivity seems to be more common in certain breeds such as Siamese, Abyssinian, and Sphynx cats.

It is important to note, however, that the sensitivity to catnip is not limited to these breeds alone. Even among cats that are genetically predisposed to responding to catnip, the level of sensitivity can vary. Some cats may exhibit a strong reaction to just a small whiff of the herb, while others may require more prolonged exposure or larger quantities to experience the same effect.

It is also worth noting that kittens younger than six months old do not typically respond to catnip, as their sensitivity to nepetalactone has not fully developed. Similarly, older cats may become less responsive to catnip as they age. In addition, some cats that are generally responsive to catnip may become desensitized to it over time, meaning that they will no longer respond as strongly or at all.

In conclusion, while certain breeds may be more likely to be affected by catnip, the sensitivity to nepetalactone is an individual trait that varies from cat to cat. It is also influenced by age and exposure to the herb. Therefore, it is not possible to say with certainty whether all cats can be affected by catnip, as there will always be some degree of individual variability.