Hold the prescription: Try these 7 natural antibiotics instead.

There’s no doubt that prescription antibiotics, such as penicillin, have made a profound difference in the treatment of otherwise fatal diseases since their discovery 80-odd years ago. However, experts have shown that as many as 20% of patients treated with antibiotics experience adverse side effects that range from mild allergic reactions to severe gastrointestinal disturbances. Because of this, more people are turning to folk medicines that include the use of natural antibiotic remedies.

Here are seven natural antibiotics—aromatic plants, herbs, spices, and their derivatives—that have been proven effective in clinical trials.

Goldenseal

Commonly consumed as a tea or taken as a supplement, the herb goldenseal (Hydrastis canadensis) is often combined with echinacea for the prevention or treatment of the common cold. It is also used in traditional medicine for the treatment of various infections related to the eyes, skin, and urinary tract, as well as for diarrhea, vaginitis, and canker sores—despite the lack of direct evidence supporting its use for these conditions.

The reasoning for this may be due to berberine, a substance in goldenseal that has been shown to kill some strains of bacteria and fungi in in vitro studies. In one study examining goldenseal’s efficacy, researchers showed that goldenseal extracts were able to stop methicillin-resistant Staphylococcus aureus (MRSA) from damaging tissue.

The authors concluded that their “data lend support for the traditional use of H. canadensis to treat skin infections,†adding that “H. canadensis leaf extracts possess direct antimicrobial activity that is due in part to the alkaloid berberine, but not canadine or hydrastine.â€

Pau d’arco

Derived from the inner bark of several Tabebuia tree species, pau d’arco—also known as taheebo or lapacho—is endemic to South America, where its earliest reported medicinal uses date as far back as 1873. Due to its reported antifungal and anti-inflammatory properties, pau d’arco is often consumed as an herbal tea for a wide range of inflammatory ailments and infections, including arthritis, fever, prostatitis, candidiasis, bacterial infections, parasitic diseases, dysentery, boils, and ulcers.

In one in vitro study, naphthoquinones, the active compounds found in some Brazilian medicinal plants including pau d’arco, demonstrated antifungal and antibacterial activity against gram-positive bacteria. These findings support those from other laboratory studies of the efficacy of pau d’arco on infections. However, further studies in humans are needed.

Myrrh

Myrrh has a rich history, dating back to ancient times. Described in both the Bible and Talmud as one of the primary ingredients in holy anointing oil, this russet- or golden-colored resin had a variety of historical uses that ranged from religious incense and insect repellent to facial treatment and kohl eyeliner. Old-world medical practitioners valued myrrh for its antiseptic and anti-inflammatory properties, and considered it to be an effective remedy for an array of ailments, including indigestion, toothaches, and even leprosy. They also used myrrh in combination with frankincense as a purifying agent to stop the spread of airborne disease and bacteria—a practice some experts believe actually has some merit to it.

In one study, for instance, the combined use of frankincense and myrrh oils was shown to be effective against select pathogens. In another more recent study, burning myrrh and frankincense incense decreased airborne bacteria by as much as 68%. The findings from these studies and those from other laboratory studies over the past two decades lend credence to myrrh’s reported antibiotic profile.

Today, myrrh is still used in Ayurvedic medicine, traditional Chinese medicine, and aromatherapy, and is included in many natural mouthwashes and toothpastes as an FDA-approved additive. According to some research, myrrh oil may aid in pain relief and the healing of mouth sores.

Oregano

Most of us are familiar with the culinary uses of oregano in olive oil-based and tomato-centric dishes, but did you know that this Mediterranean herb also has important medicinal utility as an antibacterial and antifungal agent? In a review of studies focusing on the antibiotic and antimicrobial activities of several spices and their derivatives, researchers found that oregano was among the most effective natural antibiotics against several strains of bacteria and fungi—including Salmonella, Escherichia coli, and Bacillus subtilis—and was especially effective as an essential oil.

Thyme essential oil

Like oregano, thyme is another culinary gem that has been shown to have strong bactericidal activity as an essential oil. In a study that examined the antibacterial activity of thyme and lavender essential oils on strains of Staphylococcus, Enterococcus, Escherichia, and Pseudomonas genera, researchers found that “thyme essential oil demonstrated a good efficacy against antibiotic resistant strains of the tested bacteria.†In another study that focused exclusively on the effect of thyme essential oil on standard bacterial strains and 120 clinical strains derived from patients with infections, “thyme essential oil strongly inhibited the growth of the clinical strains of bacteria tested,†according to the authors.

Neem oil

Neem oil is derived from the fruits and seeds of the neem tree (Azadirachta indica), which is endemic to the Indian subcontinent. Although neem oil has a gamut of uses in traditional Chinese and Ayurvedic medicine, it is largely prized as an antibacterial and antifungal agent, and is used for the treatment of ringworm, head lice, bacterial infections of the skin, and other skin conditions like hives, eczema, psoriasis, and scabies.

Recently, researchers have begun to study neem oil’s impact on health and disease, with a particular focus on its antiseptic properties. In one review of neem oil’s medicinal uses from prehistoric to contemporary times, researchers found evidence supporting neem oil’s strong antibacterial and antiviral profile, citing its efficacy against parasitic diseases and some sexually transmitted diseases like gonorrhea. With respect to skin diseases, they concluded that “[n]eem has a remarkable effect on chronic skin conditions. Acne, psoriasis, eczema, ringworm and even stubborn warts are among the conditions that can clear up easily when high-quality, organic neem oil is used.â€

Furthermore, in a 2016 study in which researchers studied the antibacterial effects of neem oil on 107 strains of MRSA, they found that all strains were killed upon exposure to neem oil within 12 hours, with 56 strains killed after only 1 hour of exposure.

“[Our] results are suggestive of antibacterial effect of Neem oil on multidrug resistant MRSA. Since neem oil exhibited bactericidal effect on MRSA, it may find clinical application as a topical antibiotic for MRSA infections,†concluded the authors.

Anise

Anise, or aniseed (Pimpinella anisum), is a spice with a distinct licorice-like taste that is often used as a flavoring additive in desserts and beverages. Among its many health benefits, anise has been shown to inhibit bacterial and fungal growth, making it a powerful antimicrobial agent. In a 2017 study, for instance, researchers assessed the antibacterial and resistance modulatory activity of aniseeds waste residue extract (ASWRE) and star anise waste residue extract (SAWRE) against 100 isolates of Streptococcus pneumoniae, S. aureus, Klebsiella pneumoniae, E. coli, Acinetobacter baumannii, and Pseudomonas aeruginosa. They found that both ASWRE and SAWRE demonstrated significant bactericidal activity against all of the bacterial strains tested, and were notably synergistic when used with conventional antibiotics.

“The combination between anise waste extracts and the test antibiotics could be useful in fighting emerging drug-resistant bacteria. These results suggest that both aniseeds and star anise waste residue methanolic extract (post-distillation) could be good economic sources of multidrug resistance inhibitors…Their use in combination with conventional antibiotics should be further studied for in vivo activities. This may lead to the development of much needed drug enhancing preparations,†concluded the authors.

The adverse side effects of prescription antibiotics coupled with the rising threat of drug-resistant bacteria has led many patients—and scientists—to look to the plant kingdom for answers. But while natural antibiotics may offer healthier alternatives to prescription antibiotics, they are not entirely without risk. After all, just because something is natural doesn’t necessarily mean it’s safe. Natural antibiotics should be used in moderation to reduce the risk of toxicity, and should only be used following clinical consultation to avoid any potential adverse herb-drug interactions.