In the winter, I enjoy an occasional soak in a hot bath, especially when my muscles ache after a hard day, and I often add a cup or more of Epsom salts. These seem to make the bath even more soothing and therapeutic, and I feel especially clean afterward.

Am I crazy, or is there something to this? I’m wondering about the chemistry. Are these salts absorbed through the skin, and if so, isn’t a cup of salt rather harmful? And can they cause kidney stones? I had one of those last year and wonder if this had anything to do with it. — J.G.

Answer: Magnesium sulfate (Epsom salt) is used by many people as a soak and for purported health benefits. Many people feel that they make the bath especially relaxing. While magnesium is a critically important salt, we get the magnesium we need through food nearly all the time, while magnesium supplementation is necessary on occasion, such as in people taking certain diuretics.

However, although there may be some small absorption, magnesium is not at all well-absorbed through the skin, so there is neither harm nor benefit to soaking in Epsom salts. A cup is a commonly recommended amount of Epsom salt to add to a bath.

Dear Dr. Roach:

I noticed some pain in my foot, and when I looked closely, I found a small red spot on the sole of my foot with a hair growing out right where the pain is. What is this? I thought hair didn’t grow on the sole. Is this a tumor? — I.J.M.

Answer: A hair splinter is when a cut piece of hair pierces the skin. It’s not common (I’ve only seen one case), but it is reported in medical literature. Because it is most common with freshly cut hair (which is very sharp), it is particularly common in people who cut their hair often.

Removal of the hair with tweezers immediately stops the pain. This should be done as soon as possible, since any splinter can be a source of infection. Unless you are flexible and have good eyesight, you may need a friend, doctor or nurse to do it for you.