Insect repellent: types, which to choose and how to use

Insect-borne diseases affect millions of people worldwide, causing disease in more than 700 million people a year, mainly in tropical countries. Therefore, it is very important to bet on prevention, and the use of repellents is a great solution to prevent bites and prevent diseases.

Topical repellents can be synthetic or natural, which act to form a vapor layer on the skin, with an odor that repels insects, and other measures can also be adopted, mainly in closed places, such as cooling the house with air conditioning, using mosquito nets, among others.

Topical repellents

Some of the most used substances in topical repellents are:

1. DEET

DEET is the most effective repellent currently available on the market. The higher the concentration of the substance, the longer the repellent protection will last, however, when used in children, a lower DEET concentration, less than 10%, should be chosen, which has a shorter duration of action and, therefore, it should be applied more frequently, in order to maintain protection in children older than 2 years.

Some of the products that have DEET in their composition are:

Repellent	Concentration	Allowed age	Estimated action time
Autan	6-9	> 2 years	Up to 2 hours
OFF lotion	6-9	> 2 years	Up to 2 hours
OFF aerosol	14	> 12 years	Up to 6 hours
Super Repelex Lotion	14.5	> 12 years	Up to 6 hours
Super aerosol repelex	11	> 12 years	Up to 6 hours
Super repelex kids gel	7.34	2 years	Up to 4 hours

2. Icaridine

Also known as KBR 3023, icaridine is a repellent derived from pepper that, according to some studies, has an efficiency of 1 to 2 times greater than DEET, against the mosquito Aedes aegypti.

Repellent	Concentration	Allowed age	Estimated action time
Exposis Infantil gel	20	> 6 months	Up to 10 hours
Exposis Infantil spray	25	> 2 years	Up to 10 hours
Exposis Extreme	25	> 2 years	Up to 10 hours
Adult Exposis	25	> 12 years	Up to 10 hours

An advantage of these products is that they have a prolonged action time, up to about 10 hours, in the case of repellents with 20 to 25% Icaridine concentration.

3. IR 3535

IR 3535 is a synthetic biopesticide that has a good safety profile and is, therefore, the most recommended for pregnant women, having a similar efficacy in relation to DEET and icaridine.

This product can also be used in children older than 6 months, and has a duration of action of up to 4 hours. An example of an IR3535 repellent is Isdin's anti-mosquito lotion or Xtream spray.

4. Natural oils

Repellents based on natural oils contain herbal essences, such as citrus fruits, citronella, coconut, soy, eucalyptus, cedar, geranium, mint or lemon balm, for example. In general, they are very volatile and, therefore, in most cases they have a short-lived effect.

Citronella oil is one of the most used, but it is recommended to apply it every hour of exposure. In addition, some studies prove that eucalyptus-lemon oil, in concentrations of 30% is comparable to DEET of 20%, providing protection for up to 5 hours, being, therefore, the most recommended of natural oils and a good alternative for people who for some reason cannot use DEET or icaridine.

Physical and environmental repellents

Generally, non-topical repellents are indicated as an aid to topical repellents or in children under 6 months, who cannot use these products.

Thus, in these cases, the following measures can be adopted:

• Keep refrigerated environments, since insects prefer warm environments; Use simple mosquito nets or permethrin on windows and / or around beds and cribs. The pores of the mosquito nets should not be larger than 1.5 mm; Choose to wear light fabrics and avoid very flashy colors; Use natural incense and candles, such as andiroba, remembering that their isolated use may not be enough to protect against the bite of the mosquito and that only have action when applied for continuous hours and started before the person's exposure to the environment.

These are good options for pregnant women and children under 6 months of age. See other repellents adapted for these cases.

Repellents without proven effectiveness

Although they are widely used in clinical practice and some of them are approved by ANVISA, some repellents may not be effective enough to prevent insect bites.

The bracelets soaked in DEET repellents, for example, only protect a small region of the body, up to about 4cm from the area around the bracelet, so it cannot be considered a sufficiently effective method.

Ultrasonic repellents, luminous electrical devices with blue light and electrocuting instruments have also not been sufficiently effective in several studies.

How to properly apply the repellent

To be effective, the repellent must be applied as follows:

• Spend a generous amount; Spend on several areas of the body, trying to avoid distances greater than 4 cm; Avoid contact with mucous membranes, such as eyes, mouth or nostrils; Reapply the product according to the exposure time, the substance used, the concentration of the product, and the guidelines described on the label.

Repellents should only be applied to exposed areas and, after exposure, the skin should be washed with soap and water, especially before sleeping, in order to avoid contaminating sheets and bedding, preventing a continuous source of exposure to product.

In places of high temperature and humidity, the duration of the repellent effect is shorter, requiring more frequent reapplications and, in the case of activities in the water, the product is more easily removed from the skin, therefore it is recommended to reapply the product when the person comes out of the water.