There are many major areas involved in man sexual enhancement:

Psychological
The causes of psychological sexual dysfunction in men, and it is difficult to list them all, but most often low libido is related to depression, performance anxiety, marital stress or relationship problems, life crisis, financial difficulties, religious repression, or some type of mental illness. Sexual enhancement is possible through various forms of therapy, stress release, vacation, etc.

Hormonal -- Androgens, such as testosterone, are a major component of sexual enhancement in man. Testosterone levels decline about 1 percent each year in men, which may contribute to lower male libido with aging. Testosterone also declines with age in women leading to a decrease in female libido. Women who have had surgical removal of the ovaries notice a drop in sexual interest. Sexual enhancement through replacement of androgens can be helpful in those with age related sexual dysfunction. Testosterone is available by prescription only. An over the counter hormones, such as DHEA, converts into testosterone and thus has a positive influence on libido. Pregnenolone is another over the counter hormone that may increase testosterone levels and thus enhance libido.

Vascular -- Alterations in the flow of blood to and from the penis are thought to be a common cause of male erectile dysfunction. For instance, medical conditions such as atherosclerosis (hardening of the arteries), high cholesterol, hypertension, or diabetes reduce blood flow to the penis and genital organs thus leading to difficulty with erection or genital swelling. Proper diet and exercise can reduce the risk. Additional factors that can impede blood flow include penile injury, surgery in the pelvic or abdominal area, and sitting on a bicycle too long. Men who log several thousand miles a year on their mountain bikes suffer scrotal damage that could reduce their fertility.  

Neural - Nerve damage from disorders such as diabetes, multiple sclerosis, Parkinson’s disease, and stroke affect the brain’s ability to respond to sexual stimulation. Sexual dysfunction is common in men undergoing surgical treatment for prostate enlargement or cancer.

Chemical -- Some chemicals involved in the human sexual response and libido include dopamine, acetylcholine, and nitric oxide. Sexual enhancement is quite likely through manipulation of these brain chemicals by using natural herbs. Serotonin blunts sexual enhancement.

Medical conditions that interfere with sexual enhancement in a man
Certain medical conditions reduce libido, performance, or enjoyment. These include hypertension, diabetes, high cholesterol, cardiovascular disease, peripheral vascular disease, and neurologic disorders, and insomnia.

Drugs that interfere with Sexual enhancement in men
Drugs that interfere with sexual performance in a man include some anti-hypertensives, SSRIs, sedatives, and beta-blockers. Alcohol's negative affect on libido increases with age. Smoking can reduce genital blood flow.

Man Sexual Enhancement Research Update
Exercise and weight loss may improve sexual function in obese men, researchers in Italy report. In a new study of more than 100 obese men with erectile dysfunction, nearly a third regained normal sexual function after participating in an intensive weight loss program. A natural supplement called tongkat ali can help improve sex drive.

Sexual enhancement emails
Q. i was searching for a sexual enhancement supplement and i discovered your site. At present, im taking a herbal tea, granulated it is composed of many herbs and recently i did some study on each of the herb and i found none of them
produces instant erection here they are:
1. herba epimedum epimedium brevicorrum
2. herba cyanomorum cyanomorium songarium
3.woodwardia japonica rhizoma dryptoris crassirhizomae
4. fructus polygalea soralea coryloforia
5.yang gong cao verbena officinalis
6. radix polygalea polygala tenuilolia
7.semen astragali complanati astragalus complanatus
8.pilose antler cervus nippon

i studies each and none produces instant erection or sexual enhancement, but my question is: why do i get instant erection after drinking the tea, even the very first time i tried it there was an instant erection just few minutes later,
but none of the herbs, even the no.1 in the list which is herba epimedu which i learned is horny goat weed,
this doesnt produce instant erection. So can u help me understand, is there something i missed? my question is how did the tea produce an instant erection and sexual enhancement? The tea gives me a headache, like Viagra.
   A. It is possible that the tea could have been laced with a pharmaceutical drug which is not uncommon. Otherwise, we don't have a good explanation.

Q. In the past few months I've used three different sexual stimulant products; Viapro, Golden Root Complex and V-RX V. Each of these products seems to work at enhancing my erection. However, about 30 minutes after ingesting the pill I tend to feel an increase in body temperature, some facial flushing (my face feels very hot and my lips go very red for a few hours) and occasionally some lightheadedness. Does this sound like anaphylaxis to you? Some of these symptoms seem to match those of anaphylaxis - however, I have never thus far encountered breathing problems or itching. The interesting thing is that each of these three products contain very different ingredients (if the labeling is true), so I find it remarkable that I could be allergic to all three of them! Is it possible this is not an allergic reaction and just a side effect of using the products, particularly due to the vasodilation they induce? I find these products very useful and would like to keep using them, so I am eager to find out exactly how dangerous these reactions are. If it definitely sounds like an allergic reaction with the potential of causing severe anaphylaxic shock in the future then obviously I would stop using them. Any insight into this issue would be greatly appreciated!
   A. The reactions to these product could either be due to a very high amount of sexual herbs placed in them, or perhaps they have added a Viagra like chemical to their product. We prefer a slower sexual enhancement with Passion Rx which is formulated to minimize side effects. Taking too high a dose of herbal sex enhancement pills could also increase blood pressure and cause rapid heart beat or palpitations.

Q. Which is more potent for sexual enhancement, tongkat ali or avena sativa?
   A. Tongkat ali is more potent. See also Avena-Sativa sexual enhancement herb.

November 2009
FDA Warns Consumers on Sexual Enhancement Products. Another dietary supplement is found to be contaminated with potentially dangerous ingredient The U.S. Food and Drug Administration is warning consumers that Stiff Nights, a product marketed as a dietary supplement for sexual enhancement, contains an ingredient that can dangerously lower blood pressure and is illegal. Over the past several years, the FDA has found many products marketed as "dietary supplements" for sexual enhancement that contain undeclared active ingredients of FDA-approved drugs, analogs of approved drugs and other compounds that do not qualify as “dietary ingredients.” The FDA has issued multiple alerts about these contaminated dietary supplements. Consumers and health care professionals should be aware of this problem and the health hazard it presents. Sexual enhancement products that claim to work as well as prescription products are likely to contain a contaminant. Use of such products exposes consumers to unpredictable risk and the potential for injury or even death. In the case of Stiff Nights, following a consumer complaint, the FDA determined that the product contains sulfoaildenafil. This is a chemical similar to sildenafil, the active ingredient in Viagra. Sulfoaildenafil may interact with prescription drugs known as nitrates, including nitroglycerin, and cause dangerously low blood pressure. The product is distributed on Internet sites and at retail stores by Impulsaria LLC of Grand Rapids, Mich. It is sold in bottles containing 6, 12, or 30 red capsules or in blister packs containing one or two capsules. "Because this product is labeled as an ‘all natural dietary supplement,’ consumers may assume it is harmless and poses no health risk," said Deborah M. Autor, director of FDA’s Center for Drug Evaluation and Research Office of Compliance. "In fact, this product is illegally marketed and can cause serious complications.” The FDA advises consumers who have experienced any adverse events from sexual enhancement products to consult a health care professional.