How do tattoos work? I mean, if human skin cells are always shedding and reproducing themselves, how are the pigments of a tattoo able to stay in the skin for so long?

1) What is TMJ? What kind of doctor handles this problem?

2) I have a rather odd problem. For the past several years, I have noticed that when I open my mouth wide to yawn or take a bite out of a sandwich, the right condyle of my jawbone slips laterally from the temporomandibular joint, making it difficult, and at times, painful, to close my mouth. I basically have to slip the condyle back into the socket; otherwise, it slips in by itself, which is what causes the pain.

Other than being inconvenient, this has not adversely affected me in any way that I can tell, except that I am now careful not to open my mouth completely when I yawn. I am reluctant to see a doctor about this because I cannot reproduce the situation at will, and don't know if the problem can be diagnosed or detected unless the doctor actually sees the condyle slip out.

Also, any time I have gone to Health Services, it seems that whatever the problem, they just send me home with a jar full of ibuprofen. What do you think is wrong? Is this problem serious? Does it deserve immediate attention? What type of doctor would I need to see and could I get a referral from Health Services?

Is it possible to become dependent on moisturizers?

I suffer from dry skin and each Winter go through about half a gallon of moisturizer all over my body by Spring time. It's starting to feel like my skin is getting dependent on the moisturizers, meaning that it always feels like I need them, even if it is a humid season. It's like the skin gave up on circulating its own moisture because it is expecting it from moisturizing cream. Is this just my imagination? Or should I back off on the moisturization?

I have a one half inch lump inside the back of my leg two inches above my knee (there is no visible mark on the skin). It is not painful or bothersome in any way. An acupuncturist thinks it is a cyst. If it is, what kind might it be, what kind of treatment might I get, and how necessary is it?

My question is about the cleanliness of loofahs and other body scrubbers. Since they usually hang out in the shower where there is constant warmth and moisture, wouldn't they grow bacteria? How often should they (scrubbers) be changed or how do you clean them? The reason I ask is that I am experiencing some hives, and the only thing I can think that is causing it might be the scrubber gloves in my shower.

Is it dangerous to wax or use a chemical depliatory such as Nair on areas of the skin that have moles? I've seen warnings on some labels regarding this. What could happen to the moles?

1) I read the information on your website about knuckle cracking, and I was wondering if it applies to cracking backs and necks. I know that people often have their backs cracked by friends, etc. because it feels good and seems to relieve tension. Also, when my neck feels tight, I often turn it from side to side until it cracks and feels better. I've heard that chiropractors do some version of this, and call it "realignment." Is this safe? Is there a right or a wrong way to crack a back or neck? Is cracking your back/neck actually therapeutic in some way?

2) As a college student, I sometimes spend long hours reading books or looking at computer screens, and often my neck gets stiff. Like many of my joints that get stiff, sometimes I crack my neck, like I would crack my knees or fingers when they feel stiff. I often wind up doing this several times a day.

My question is, could I do irreparable damage to my spinal system if I continue using this method to soothe a stiff neck? Could I wind up a paraplegic if I continue to crack my neck? Leak spinal fluid, etc.?

I was thinking of buying a face powder that says it has an spf of 30. It seems convenient to have a powder sunblock since lotions make my oily face greasy. However, I was wondering if this powder will even be effective as a sunblock since I heard that some moisturizers and other products that advertise an added SPF sometimes don't have a high enough concentration of sunblocking ingredients to make it effective. I would like to know what do you think before I make my purchase.

When is a person with a cold contagious? A couple of friends, who are put off when I keep my distance from their sneezing and coughing, insist one is only contagious a week or so before symptoms appear. In the back of my memory is the idea that one remains contagious until a few days *after* primary symptoms disappear. I'm not usually so concerned about this, but I'm coping with a couple of other annoying health problems and want to try to avoid adding a cold or flu, to boot. I do the usual things news shows recommend — eat well, wash hands frequently. But when should one avoid others who have colds, or when should one stay isolated at home when one has a cold (or flu)?