Probably the most common form of yeast infection is thrush, where the infection is in the vagina. But men can suffer from penile yeast infection too, although much rarer than thrush in women. Yeast infections are caused by a fungi called Candida, much of it by a particular strain called Candida albicans, although other species can also cause yeast infection. Candida albicans exists naturally in the human body quite peacefully along with other flora without any problems, because it is kept in check by the body's friendly or beneficial bacteria.
It just loves to live in the warm, dark, moist areas of your body, which is why it is most often found to be present in the vagina, mouth, blood, gut, etc. But it can also be discovered on your skin, especially under the skin folds, armpits, crotch, etc., which can be more moist.
Another name for yeast infection is Candidiasis, and sometimes just Candida. So what causes yeast infection? Well, the conditions have to be just right for the Candida albicans to multiply and grow out of control. And basically, this means that your body's good bacteria are insufficient in number to keep the Candida flora in check.
This can happen due to a compromised immune system, diabetes, overuse of antibiotics and / or steroids, poor nutrition, body pH changes, being under stress, some medications, and so on.
Generally speaking, the presence of 'overgrowing' Candida fungi is signaled by severe itching, burning sensation, tingling, redness, etc. In terms of vaginal thrush this could have been accompanied by a cottage cheese-like discharge, painful or impossible intercourse, and pain when urinating.
In terms of oral yeast infection, you may notice white / creamy raised patches over the tongue and mucous membranes. When these are scraped away you'll usually find bleeding underneath. Penile infection will exhibit blister-like sores on the head and / or foreskin.
Other surprising symptoms include pain or swelling in the joints, muscle aches, drowsiness, fatigue, dizziness, lack of coordination, fluid retention, poor concentration, poor memory, depression, irritability, mood swings, and cravings for alcohol, sugars, and carbohydrates.
Typical treatments are over-the-counter or prescribed drug-based medications using creams, suppositories, lotions, sprays, lozenges, liquid suspensions (swish and swallow), etc., depending on the locality of the Candidiasis.
The problem with mainstream treatment is that it really only addresses the symptoms and not the underlying causes of the Candida overgrowth. Plus, being drugs, the Candida can build-up a resistance to them, which means that the infection just keeps on coming back. Which is why more and more yeast infection sufferers are turning to natural cures for their condition.