We looked at the hard evidence to see if rosemary or its derivatives were effective as a natural mosquito repellent and/or mosquito killer.
Summary of Scientific Research
Rosemary (scientifically known as Rosmarinus officinalis) is perennial herb native to the Mediterranean region but is grown around the world today in cool and moderate climates. Though rosemary blossoms with fragrant white, pink, purple, or blue blooms, it is mostly prized for its needle-like evergreen leaves, which are harvested and used in everything from cooking to perfumery.
Several anecdotal sources also attribute insecticidal qualities to rosemary, both in it pre- and post-harvest forms. This appears to be a causational attribution relating to the strong odor produced by rosemary, which would then (in theory) prevent mosquitos from smelling (and thus targeting) those in the proximity to rosemary bush or wearing rosemary oil.
Unfortunately, the current body of scientific evidence is unable to support these claims. Few (if any) scientific studies have been conducted to test rosemary’s effectiveness in this domain. In fact, one of the only data-based analyses of rosemary’s uses as a natural mosquito repellant came in the form of a safety rating, based on concentration. A 2011 meta-analysis of that study found rosemary to be safe for human use at up to 36% concentration and highlighted the active methyl eugenol in rosemary’s oil profile as a carcinogen (1).
Beyond this, most “evidence” in favor of rosemary’s effectiveness in deterring mosquitos comes from digitally recounted anecdotal users, with rosemary’s essential oil and basic plant forms both recognized for these properties. While these accounts may be truthful at their core, their veracity is difficult (if not impossible) to confirm without controlled laboratory and field testing.
While rosemary remains a lovely herb to grow for use in the kitchen, it likely won’t serve you well if you are in search of a natural mosquito repellant. The general lack of testing relating to rosemary’s use in this domain makes it a questionable option, especially when broadly-tested options like lemon eucalyptus remain available. Unless further evidence becomes available in the immediate future, consumers should continue to turn elsewhere when choosing a natural insect repellant.
Along the same lines, safety stands out as a worthwhile concern when it comes to rosemary. One of the only studies relating to rosemary’s use in this domain returned results that point to potential hazards posed by one of the plant’s active ingredients. Paired with its unproven track record, this carcinogenic hazard is a certifiable reason to pass over rosemary.
Forms of Rosemary and Where to Get it
- Rosemary plants – Unlike many plant-based mosquito repellant options, rosemary can be grown in an at-home herb garden, both indoors and outdoors. While the seeds (available online) can take some time to germinate, they will eventually thrive if allowed to take root in well-drained soil that receives full sunlight.
- When it comes to harvesting rosemary, trim individual stems off the tree and store them upside down in bunches to dehydrate. Once dried, pick the leaves and preserve them in vinegar or an oil (if used for cooking) (2).
- Essential Oil – Despite its unproven effectiveness when it comes to blocking mosquitos, most proponents of rosemary call for its essential oil form to be either applied to the skin or deluded into a spray. In either case, this oil can be found online with ease and used in accordance with the labeled safety instructions.
2 – Bonnie Plants. How To: Growing Rosemary.
Other Plants & Herbs as Mosquito Repellents
Checkout our analysis of other plants & herbs as natural mosquito repellents: