My son has (9) has dry fingernails?!

My son has (9) has dry fingernails?

my 9yr old son has 1 finernail on each hand that is strange,like dry and hard,it seems to attach to the skin on the finger at the end. he doesnt like me cutting it,says it hurts.it has been like this since he was about 2 and he has seen the dr then, and he took a piece of nail, for tests but nothing came of it.i thought it would have gone by now.all the other nails are fine.does anyone have any ideas ?

2 weeks ago
yes its the same finger on each hand

I think it odd that the "dryness"affects just one finger on each hand. Is it the corresponding finger of both hands? Or say a thumb and a pinkie(little finger).
I would try some warm oil, castor or olive oil might be good. Otherwise something taken internally as there may be a deficiency of nutrients. e.g .a lack of Vitamin A and calcium or insufficient B12.
Vitamin A can be found in Fish Liver Oils and green and yellow fruits and vegetables while good sources of Calcium are dairy foods, Salmon(with bones) sardines, seafood, and green leafy vegetables. Also in almonds, asparagus, blackstrap molasses, brewer's yeast, brocoli, buttermilk. cabbage, carob, cheese, collards, dandelion greens,dulse, figs, filberts, goat's milk, kale kelp, mustard greens, oats parsley, prunes, sesame seeds, tofu, turnip greens, whey and yogurt.
Sources for B12 are blue cheese, cheese,clams, eggs, herring, kidney, liver,mackerel, milk, seafood, and tofu. Not however, found in vegetables

Hope you can find something in this that a nine year old will eat. AND which will help him.. Good Luck!