What does it mean when a dog shows lipstick?

A dog showing "lipstick" means it is in heat. This is a cryptic way of saying that a male dog's genitals are congested. A male dog in heat will urinate everywhere and leave his scent to attract the female dog; he also likes to climb astride the female dog, or use his front legs to grab a person's arm, and rub the inside of his hind legs against the person's leg corners. Some dogs will try their best to run out and find a suitable mating partner.

What should you pay attention to when your dog shows "lipstick"

Male dogs do not have a fixed estrus period. Generally speaking, male dogs become sexually mature at 11 months old. They will mate instinctively, but for the sake of the male dog's own health and the genetic protection of his offspring, it is recommended that the male dog be bred after one and a half years old, because it takes one and a half years for the male dog's body to mature.
The estrus of male dogs is not as regular as that of female dogs. Male dogs will also passively go into estrus when there are female dogs in estrus around. If you are an owner who does not want to breed, you can take your dog for sterilization surgery around 6 months old, making sure to avoid the dog's estrus period.