The question of how long it takes to develop HFMD after contact with a person with HFMD involves the incubation period of HFMD. If you are infected with the pathogen in question after contact, you will have an attack of HFMD on your own, which is called the incubation period and is usually 3-7 days. It is also possible to be infected and not develop the disease, because many of the pathogens that cause HFMD can infect a person without causing symptoms of HFMD, and the infection may only be insidious. It is also possible to develop herpetic angina instead of HFMD. The difference between herpetic angina and HFMD is that red papules and herpes do not appear on the hands and feet, but the incubation period for both is actually about the same. After contact with HFMD, it is also possible not to be infected, and in this case there will be no illness.