Hope this will be of some help, and not get you paniced or excited. I never have bitten my nails, I am 51 years young, I occasionally use nail polish, have used acetone and non-acetone nailpolish remover, I am female, O+ Blood type, slim build since I was 12, and I started noticing ridges on my nails (even toe nails) about 7 years ago. I have seen Doctors for my spine, had my gal bladder removed about 5 years ago, and still had the same pain in my back, and my fingernails got worse. Recently I had rib pain, odd for me, so the Dr. did a CT scan, compared it to the scan from 5 years ago when I had my Galbladder removed, and detected Lymphoma Cancer. I had previously been told by a Dr. the ridges might be a side effect from Reynaulds Syndrome (Burgers syndrome in men) because my knuckles were reddish compared to the rest of my hands as well, a sign of Reynaulds, but come to find out I am stage 4 with cancer in my lymphatic system AND it is in my Bone Marrow. I am apt to think the ridges may be an early indication of possible bone marrow/Lymphoma. Get to your Doctor and demand a CT scan, or a PET scan. It is better to be safe than sorry. My prognosis is not good since I have B Cell (sub category) Mantle cell cancer. Please don't just depend on answers from laymen, or from others, seek a medical opinion from a real Doctor (I didn't until it was too late). Also, symptoms of lymphoma include mild night sweats to drenching night sweats (I had mild sweating on my forehead on occasion, nothing to alarm anyone) and mild itching of the skin (like you feel a hair tickeling and brush your arm off scratch your head thinking it must be time to shampoo, feel like something is on your face so you swipe your hand across that, maybe feeling like a small sting on your calf, so you run your hand across it... etc. Nothing major) and that is it... Not much of a symptom list for something so frightening and so deadly. Don't take any chances. Have a CT scan done, and in 6 months or a year, have another and have them compared. Better to be safe than sorry. I hope this helps.