Chihuahuas can usually climb stairs easily, as long as they don't have any orthopedic or neurological issues. However, it's best to avoid introducing puppies to stairs until they are 12 months old to prevent injuries. Older Chihuahuas should also avoid stairs due to decreased muscle mass and fragile bones. Chihuahuas with genetic health problems should be kept away from stairs to prevent worsening their condition. To protect Chihuahuas from stair-related injuries, owners can use baby gates, monitor their dogs for signs of discomfort, and provide better grip on the stairs with carpet or runners.