But this year a new strain of the virus is causing more serious symptoms.
Health experts say hand foot and mouth is a viral disease. It is contagious, and doctors say usually goes away after a short time.
But this year the symptoms are taking longer to heal and are more painful.
At Fresno's Learning Tree, five children have picked up Hand, Foot and Mouth Disease this year. Cyndi Gomez says the organization does everything possible to prevent the spread of the illness.
"It's very easy because children at a young age their hands are in their mouth, their hands are all over the toys, all over the furniture because it's very easy," Cyndi Gomez of The Learning Tree said.
Health experts say the viral disease usually infects babies and toddlers and often spreads through saliva at daycare centers.
It causes a fever and contagious fluid-filled sores to grow on children's palms and the soles of their feet. Painful blisters can also sprout inside their mouths.
"The young children who are on bottles, with a mouthful of sores parents sometimes don't realize why they are not eating. They are thinking 'oh, my child's not hungry' but it's actually the sores hurting," Gomez said.
This year Dr. Edward Moreno and his staff at the Fresno County Health Department are seeing a new strain of the virus in the Valley. That strain, they say, is more serious.
"Pediatricians are also reporting that the lesions are more painful than the typical Hand, Foot and Mouth Disease and the rash is staying a little longer than usual," Dr. Moreno said.
In some cases the rash is even leaving scars and is more contagious.
"What we are seeing this year is that there are some older children and younger adults who are actually getting the disease from the babies," Dr. Moreno said.
Doctors say parents can give children Tylenol to help them deal with sores that hurt and keep them away from other children.