Hello Dr. I Have A Son And A Daughter That

Hello Dr. I have a son and a daughter that has a split near the root of the hand fingernails, One week ago my 12 years old son got the split and we thought he hit his finger on something and today we discovered our five years old daughter got the same split on her hand finger nail and my son got the second split on his second finger please note that we live in a farm and we raise a lot of outside cats rabbits and pigeons, and only my son touches these animals with his hand I want to know if touching these animals is the reason and I want to know if this is A fungus bacterial issue or it has something to do with their diet also know that we have a very healthy diet routine I am very concerned that this is contagious. Today I minced some garlic and I applied it on the nail and then and then wrapped it I don't know if it's a good thing to do and if you can prescribe any medication for my kids i'll be very thankful