Onslaught is a broad spectrum pesticide that contains the active ingredient esfenvalerate, also referred to as S-fenvalerate.  While this main ingredient has been used in other types of pest control products, Onslaught provides a unique formulation that offers much greater residual control against the target insect pest.  This formula is has no odor, so it can be sprayed both indoors and outdoors.
Onslaught is unique due to the fact that it is micro-encapsulated.  This means the product can last much longer overall, which in turn provides much better control for a variety of insects.  Most pesticides in this category are classified as emulsifiable concentrates (EC), which provide up to thirty days of residual coverage indoors.  Onslaught typically lasts as much as two to three times longer when applied to control crawling pests indoors.
Because Onslaught is micro-encapsulated, it is also highly concentrated.  A mere one half ounce is needed per gallon of water to treat a wide variety of insects.  The recommended “clean out” rate is just one ounce per gallon of water, and is typically used for very high infestations or when spraying is needed for pests that are difficult to control.  Some of the most commonly treated pests with Onslaught include: cockroaches, fleas, ticks, termites, and spiders.
Toxicity of Onslaught
Although Onslaught is a very effective form of pest control, it does not come without its hazards, just like all other pesticides. Prior to drying which takes around 3 minutes outside and 20 minutes inside  This chemical is considered to be a moderate eye and skin irritant, and it is also harmful if absorbed through the skin.  It has been known to cause burning or tingling when in contact with skin.
Onslaught is harmful if swallowed, and some material can get into the lungs if ingested.  High levels of inhalation can cause moderate to severe respiratory and nasal irritation.  There are no known chronic effects of the use of this product, nor are there any known carcinogenic properties.  In order to minimize the potential of side effects, it is important to wear protective clothing, eye-wear that protects the eyes, and a full face shield while applying Onslaught.
Environmental hazard
Onslaught is considered to be highly toxic to fish and other forms of aquatic invertebrates.  This product should never be applied to water, and should never be applied where runoff could affect water.  Waste runoff should never be allowed to come into contact with waterways of any kind, especially lakes, streams, ponds, or oceans.  Waste runoff from the cleaning of equipment should also not be allowed to enter any type of sewer system without first notifying the local sewage treatment plant.