DEET (N,N-diethyl-meta-toluamide) is a common active ingredient found in many insect repellents. It is known for its effectiveness in repelling a wide range of biting insects, including mosquitoes, ticks, fleas, chiggers, and flies. Here are some important properties of DEET:

1. Repellent action: DEET acts as a repellent by interfering with the insects' ability to locate humans and other hosts. It masks the body's scent and makes it difficult for the insects to detect and home in on individuals.

2. Effectiveness: DEET is highly effective in preventing insect bites when applied to the skin or clothing. It has been widely used for several decades and is considered one of the most effective insect repellents available.

3. Duration of protection: DEET offers long-lasting protection against insect bites. The duration of effectiveness can vary depending on factors such as the concentration of DEET in the product, temperature, humidity, and individual factors like perspiration.

4. Concentrations: DEET is available in various concentrations ranging from 5% to 100%. Higher concentrations generally provide longer-lasting protection, but it's important to follow the instructions on the product label and avoid excessive use.

5. Safety: DEET has been extensively researched and is considered safe when used as directed. However, it is recommended to avoid applying DEET-based products directly on broken or irritated skin. It is also advised to avoid applying DEET to the hands of young children, as they may rub their eyes or put their hands in their mouths.

6. Compatibility: DEET is compatible with most clothing materials, but it can damage certain types of plastics, synthetic fabrics, and painted or varnished surfaces. It's important to avoid direct contact with these materials when using DEET-based products.

7. Environmental impact: DEET is relatively safe for the environment when used as directed. However, it can be toxic to aquatic life and should be used responsibly, avoiding excessive application near bodies of water.