Are they harmful to children and pets?

Summer is increasingly associated with mosquitoes. What used to be a nuisance for vacationers in tropical countries has now become a real problem in cities like Rome, Athens, Barcelona, ​​Marseille or even Stockholm.

What plants will help repel mosquitoes


Climate fluctuations, changes in water management and other environmental factors are causing an increase in mosquito activity in many parts of Europe. As a result, mosquito control and the prevention of mosquito-borne diseases are becoming a public health issue across the continent.

Mosquitoes are not just a nuisance. Their bites can transmit diseases such as dengue fever, malaria, West Nile virus and Zika virus, which pose a significant risk to public health in various regions of the world. In response to this threat, the use of mosquito repellants has become common in homes with children and pets. However, despite their usefulness in preventing mosquito-borne diseases and bites, there is growing concern that these products may have adverse health effects on the most vulnerable populations.

What are mosquito repellents made from?

Only female mosquitoes suck blood. They use this extra supply of protein to be able to lay eggs, and to this end, evolution has endowed them with a sophisticated sucking mouth capable of piercing the skin. Most mosquito repellents do not kill these insects, but instead interfere with some of the mechanisms that mosquitoes use to locate their prey.

Mosquitoes are very sensitive to CO2, which is exhaled by humans and other animals during respiration and is their main mode of localization. They are sensitive to temperature and are attracted to a warm body, as well as to certain odors and pheromones emitted, in this case, by the human body. Some compounds, such as lactic acid and uric acid, are particularly attractive to mosquitoes.

Mosquito repellents are designed to prevent mosquito bites, not kill them, and their effectiveness lies in the active ingredients and other compounds they contain. Some of the more common ingredients are:

  • DEET (N,N-Diethyl Meta-Toluamide): One of the most widely used insect repellents in the world, it confuses mosquitoes’ olfactory receptors, making it difficult for them to find their prey. It is also the most efficient.
  • Picaridin (Icaridin) and IR3535: Synthetic repellents considered to be a safer alternative to DEET, with a similar mechanism of action but less effectiveness.
  • Essential oils and natural repellents: Essential oils of eucalyptus and citronella, peppermint oil and lavender oil are used as natural repellents because mosquitoes are theoretically repelled by their scent.

Effects of mosquito repellents on children

Children are particularly vulnerable to mosquito bites due to their delicate skin and limited ability to avoid contact with mosquitoes. At the same time, questions arise as to whether they are also more sensitive to the possible effects of mosquito repellents.

Studies have shown that both DEET and other ingredients used in repellents are highly safe at the concentrations they are sold at (otherwise they would not be allowed). Even in countries where there are endemic diseases such as Zika or malaria, it is considered safe to use repellants twice a day for children under 12 years of age. Side effects are rare and are limited to allergic reactions and dermatitis.

Another very different case occurs when children accidentally ingest these products, as even a small dose can cause neurological damage in them. Other studies have shown that DEET is no more toxic to children and pregnant women than it is to other adults.

Effects of Mosquito Repellents on Pets and Other Animals

DEET has a relatively low toxicity to animals, especially when applied to the skin, but as noted above, at sufficiently high doses and when inhaled or, worse, ingested by animals, it can cause signs of neurotoxicity. Studies in dogs, cats, and mice have shown that even when taken orally, effects appear at very high doses, from 100 to 500 mg per kilogram of body weight. The doses required to absorb these amounts through the skin will be much higher.

The possible impact of repellents such as DEET on wildlife has also been discussed, especially in aquatic ecosystems, where this compound enters with urban sewage or soil. However, DEET degrades in water within a few days, and its low toxicity makes it unlikely to affect aquatic life except for an uncontrolled spill.

Are effective mosquito repellents more toxic?

The quick answer is yes (especially to mosquitoes), but almost all compounds, including table salt, are toxic when taken in sufficient doses. An exhaustive study in China (another country with a tiger mosquito problem) looked at the main repellents on the market, including repellents with herbal ingredients that are considered non-toxic and contain menthol, eucalyptus or citronella.

For the study, people had to stick their hand into a cage full of mosquitoes while scientists measured how many of those insects landed and how long the hand was protected with repellents. Common repellents such as DEET, picaridin or IR3535 were considered “mildly toxic” in the study. As we saw earlier, toxicity occurs primarily in cases of accidental ingestion.

What about efficiency? In this study, repellents with higher concentrations of DEET were the most effective, as measured by the number of hours the product kept mosquitoes off the volunteers’ skin (up to almost four hours). The best of them contained 15% and 10% DEET, respectively.

Further down the list were repellents with 20% and 15% picaridin, and in the tail one could find repellents containing only herbal ingredients, which provided a much shorter duration of protection (less than an hour) and repellents with IR3535. We were also able to verify that when mixing ingredients such as DEET and eucalyptus oil in one of the brands, the effectiveness was even higher than when using only DEET.

In a recent publication with recommendations for doctors, given the risk of tropical diseases spread by mosquitoes due to climate change, the use of repellents is recommended as a preventive measure.

For people who are concerned about the (very rare) side effects of repellents, be aware that higher strength compounds and herbal extracts inherently have similar repellency to the most widely used DEET. much shorter. This means that the product will have to be applied more frequently.

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