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Last updated September 5, 2020. 9 minute read

What is Spanish fly? Does it work like Viagra?

Spanish fly is a common name for an insect that is purported to have sexually stimulating properties, which can likely be attributed to a toxic substance it contains called cantharidin. Cantharidin’s reputation for being an aphrodisiac likely comes from reports that its effects on blood vessels could cause priapism, a painful, persistent, and dangerous erection lasting more than four hours.

Linnea Zielinski Written by Linnea Zielinski
Reviewed by Yael Cooperman, MD

What is Spanish fly, and does it work?

The word aphrodisiac, which we use to describe substances that increase sexual desire, is derived from the name of the Greek goddess of love, Aphrodite (Kotta, 2013). Man has been hunting for an effective one since at least the time of the ancient Greeks. Along the way, there have been many contenders, some of which still have a reputation (chocolate and raw oysters) to those long-forgotten (Bufo toad) (West, 2015). If it weren’t for a controversial mention in an old Bill Cosby special, “Spanish fly” may well have been one that fell into obscurity.


  • Spanish fly is a common name for an insect that is purported to have sexually stimulating properties when consumed by mouth, an effect that can likely be attributed to a substance called cantharidin.
  • Cantharidin is extremely toxic and can cause serious injury or death when ingested.
  • The idea that Spanish fly has some aphrodisiac function likely stemmed from the fact that its effects on blood vessels can cause priapism, a persistent and potentially dangerous erection.
  • Under no circumstances should a person ingest Spanish fly or anything that claims to contain Spanish fly or cantharidin.

If you ever come across a product that claims to contain Spanish fly, steer clear. Spanish fly is a common name for an insect that is purported to have sexually stimulating properties, which can likely be attributed to a toxic substance it contains called cantharidin. These insects have been used in traditional medicine in China for over 2000 years (Wang, 1989). Cantharidin’s reputation for being an aphrodisiac likely comes from reports that its effects on blood vessels could cause priapism, a painful, persistent, and dangerous erection lasting more than four hours (Till, 1981).

Cantharidin is extremely poisonous and can cause injury or death when ingested. There are reports of cantharidin poisoning and death at varying amounts, leading some researchers to believe that even small quantities can be deadly (Nickolls, 1954). Reports of victims of cantharidin poisoning aren’t ancient history, either. A 23-year-old ended up in the hospital after eating one of these beetles as part of a bet in 2013 (Cotovio, 2013). There are still products that claim to contain Spanish fly on the market today, though cantharidin is not approved by the U.S. Food and Drug Administration (FDA) (Del Rosso, 2019). 


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No matter how adventurous you are, though, you should never ingest Spanish fly or anything that claims to contain Spanish fly or cantharidin. Reported side effects of ingesting cantharidin include miscarriage, priapism, convulsions, bleeding, including vaginal and rectal bleeding, vomiting blood, kidney damage, seizures, heart problems, blood in the urine, and a very dangerous condition called disseminated intravascular coagulation (DIC), where blood clots start to form throughout your body (Till, 1981; Karras, 1996). Ingesting cantharidin can be fatal.

What are aphrodisiacs?

We tend to think of aphrodisiacs as substances that increase sexual desire, but the term isn’t particularly well defined. Some people believe that these substances (which range from chocolate to raw oysters to illicit and exotic plants and animal products) can increase a person’s potency, libido, or sexual pleasure. And although a long list of substances that come from plants and animals have been considered and used as aphrodisiacs in traditional medicine, there is little or no science to back these claims up (Kotta, 2013). But that hasn’t stopped scientists from keeping the search going. Some of the purported aphrodisiac herbs we know the most about are:


Maca root is from the highlands of Peru and may increase sex drive in men. In one study, men between the ages of 21 and 56 reported increased sexual desire after eight weeks of maca supplementation, although their testosterone levels didn’t increase (Gonzales, 2002). There’s also some evidence that maca may help improve sexual dysfunction in women caused by antidepressants, though a meta-analysis of past research found there wasn’t enough evidence to make any certain claims about how this root may affect sexual functioning (Dording, 2015; Shin, 2010).

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Tribulus terrestris

This plant, which is also called Bindii, may help erectile function and libido (sex drive), but only at certain doses. One study didn’t see any positive effect from 800 mg Tribulus terrestris, but another noted significant improvement in erectile function, sex drive, and satisfaction with sex in patients given a total of 1500 mg a day (Santos, 2014; Kamenov, 2017). 

Horny goat weed

This plant, which is found mostly in China and the Middle East and is also known as barrenwort and ying yang huo in Chinese, has been used in traditional Chinese medicine for centuries. While the claims are pretty substantial, there’s little evidence that it works for anything at all. Horny goat weed does contain a compound called icariin, which seems to have the same chemical effect (at least in the lab) as prescription medications like Viagra, Levitra, and Cialis, making it a promising option (Dell-Agli, 2008), but it has yet to be proven effective as a clinical treatment for ED in humans. 

Ginkgo biloba

Ginkgo biloba is one herbal supplement that has piqued people’s interest for its ability to relax smooth muscle tissue and increase blood flow. Since these factors are crucial in a person’s ability to get and maintain an erection, it’s definitely an area of interest. But alas, human studies are lacking. One small study found that oral supplementation with ginkgo extract may help restore spontaneous erections in some men whose ED was confirmed to be caused by obstructed blood flow (Sohn, 2015).


Damiana, a small flowery plant native to the southern United States, may help increase sex drive in some women. Researchers found that the herbal supplement improved the frequency of sexual intercourse in pre- and perimenopausal women and significantly improved sexual desire in postmenopausal women (Ito, 2006). In men, damiana acts similarly to sildenafil (Viagra) to boost blood flow—but so far, most studies have shown sexual improvement in rats, not humans (Estrada-Reyes, 2013). One study showed significant improvement in erections in men after 12 weeks taking an herbal supplement that contained damiana in addition to a range of other herbs with purported aphrodisiac properties. While the treatment was more effective than placebo at improving sexual dysfunction, it would be impossible to attribute the results to damiana specifically (Shah, 2012).

Red ginseng or Korean ginseng

Ginseng may help those with erectile dysfunction. This dietary supplement “significantly improved erectile function” compared to placebo, according to researchers behind a 2018 meta-analysis that considered 24 controlled trials involving 2,080 men with ED. They concluded that the herb may be an effective erectile dysfunction treatment but also called for further research with larger sample populations. The researchers also noted that the trials they looked at were formatted differently—some looked at the effects of just one herb while others used combination therapies—so more large scale research would be the next step to verifying their findings (Borrelli, 2018).

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Yohimbe is the common name for a species of tree found in central Africa from which the active chemical, known as yohimbine, is derived. Used in West African traditional medicine as an aphrodisiac, it is a popular ingredient in various supplements promising to improve male virility. And while human studies on yohimbine for ED in humans are hopeful, research is limited. One small study found that it helped some men with mild erectile dysfunction successfully achieve and maintain an erection long enough to have penetrative sex (Guay, 2002). 

Medical options for improving sexual function

The first-line treatment for erectile dysfunction is a class of medications that includes drugs like Viagra (Park, 2013). Viagra, Cialis, Levitra, and the generic versions of these medications are examples of PDE5 inhibitors. Available only by prescription, these drugs improve blood flow to the penis in order to improve erections in patients with ED (Dhaliwal, 2020). Undeclared and, therefore, unregulated sildenafil has been identified in over-the-counter male enhancement supplements, which can be purchased in gas stations and online.

Sildenafil is a powerful drug, and its unregulated inclusion in pills is dangerous. There’s no knowing the quantity or quality of sildenafil in these pills, meaning they may cause serious potential side effects that can even be deadly when taken in doses that are too high, taken by people with certain health conditions, and when unwittingly combined with certain medications.

PDE5 inhibitors are not the only option to treat ED, though. Devices such as the vacuum constriction device (VCD), penile injection or intraurethral suppositories, and penile prosthesis are all also current therapies for people with ED (Stein, 2014). If your healthcare provider finds that your ED is caused by low testosterone levels, they can also prescribe testosterone replacement therapy (TRT).

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In many cases, ED may be caused by an underlying condition. Men who have sedentary or less active lifestyles are more likely to experience ED than their active counterparts (Janiszewski, 2009). Medical conditions that affect blood flow or cause poor circulation may also cause ED, such as cardiovascular disease (CVD) (Yafi, 2016). Hormonal issues, such as diabetes, and neurological conditions, such as Parkinson’s disease, may also cause erectile issues (Burnett, 2018; Bronner, 2011).

Conditions such as depression, low-self esteem, and stress have all been shown to contribute to the development and persistence of ED, as well (Davies, 2012). Properly diagnosing any underlying conditions and receiving optimal treatment can be the first step towards improving ED (Rosen, 2001).