Many people with chronic illness have many issues with their hair, skin, and nails. All of these body parts get food from the blood supply inside your body and many can send you small little messages that something inside your body isn't working right. If your hair is healthy and growing fast that means you are healthy and you should pat yourself on your back. You are doing great!
Many people have experienced ridges in the fingernails and toenails due to stress. This is how our bodies compensate for how we handle severe stress even when we don't always think it's that bad. Other people can lose patches of hair called alopecia. In both cases things generally go back to normal once the stressful situation has been demolished, and you are relaxed.
Medications have an intense effect on the hair almost as much or maybe even more then some of the illnesses. Post surgery some chemical services received may not take or be resistant due to the anesthesia. Blood thinners are another culprit. They tend to make the hair impossible to perm on certain people. Steroids sometimes cause your hair to go curly. Chemotherapy has a mind of it's own depending on the individual, sometimes your hair comes back curly with a straight perimeter, and then sometimes you just have curly hair or straight. Other times the color can come back completely different. If you are on a medication all the time it is definitely recommended that you ask your stylist to clarify your hair prior to your color service. This will hopefully remove any medicinal coatings and allow you to receive 100% coverage. If you are getting a perm they always clarify you prior too but sometimes they can get products that go a little further and remove more. This will hopefully remove enough medicinal coating so you can get your hair permed. Some meds are good though. People with thyroid issues may have thinning hair until their doctor gets their dosage correct and then their full, thick hair should come back in like crazy. If you are experiencing any thinning issues then you should talk to your doctor immediately.
Alcohol and non-prescribed drug use can lead to thinning, weak hair that will not take color properly and can sometimes even get damaged easily whether it's chemical or mechanical. Sometimes you don't even notice your hair is thinning, until its too late.
If you have very thin hair then you should definitely wear a hat that has UV protection when you are at the pool or the beach. Really you should wear it anytime you are going to be sitting in the sun. This will protect your scalp from sun damage. Often times we sunblock out entire body and don't ever think twice about protecting our scalps. Sometimes over exposure can lead to skin cancer.
Last but not least, eat your vegetables! Eating healthy will help improve the health of your hair. Vitamins are great too. Biotin is another great supplement for thicker, fuller hair, and be bought at pretty much any vitamin store in town.