Pepper spray, also known as OC spray (from "Oleoresin Capsicum"), is a chemical compound that irritates the eyes to cause tears, pain, and temporary blindness. It is used in policing, riot control, and personal self-defense, including protection against animals.

The active ingredient in pepper spray is capsaicin, which is derived from the fruit of plants in the Capsicum genus, including chilies. Capsaicin is an inflammatory agent, affecting the mucous membranes in the eyes, nose, throat, and lungs, leading to immediate closure of the eyes, difficulty breathing, runny nose, and coughing. The intensity of the effect can vary based on the concentration of capsaicin, the spray's formulation, and the distance from which it is deployed.

When sprayed into the face, pepper spray causes the capillaries in the eyes to dilate, resulting in temporary blindness, while exposure to the skin causes a burning sensation. The effects can last from 15 minutes to an hour, giving the user time to escape or take control of a situation. Despite its incapacitating effects, when used properly, pepper spray is considered a non-lethal weapon, with a low risk of long-term health consequences.

The mechanism by which pepper spray works involves the activation of TRPV1 (transient receptor potential vanilloid 1) receptors. These receptors are sensitive to heat and acidity, and when activated by capsaicin, they send signals to the brain that mimic the sensations of extreme heat and discomfort, triggering the body's defense mechanisms mentioned above.

Because of its potency and the immediate incapacitation it can cause, training and regulation regarding who can carry and how to properly use pepper spray vary by jurisdiction. Users are typically advised to aim for the face of an assailant, particularly the eyes and nose, and to be mindful of wind direction to avoid self-contamination.

Pepper spray, also called OC spray from "Oleoresin Capsicum," is a spray that makes your eyes tear up, hurt, and even make you temporarily blind. Police, in riots, and people who want to protect themselves or keep animals away use it.

Laws regarding pepper spray vary by location, so it's important to check local regulations. In general, pepper spray is legal for self-defense purposes in all states, but there may be restrictions on its size, concentration, and where it can be carried.

To use pepper spray effectively, aim for the attacker's face and eyes, and spray in short bursts. It's important to practice using the spray so you can quickly and confidently deploy it in a threatening situation.

After using pepper spray, move away from the attacker to a safe location and try to alert the proper authorities. Remember to wash your hands and any contaminated clothing to avoid getting the spray on yourself or others.

Pepper spray expires for a few key reasons which all boil down to the degradation of its active components and the integrity of its container over time. Here's a detailed explanation:

1. Degradation of the Active Ingredients: Pepper spray is made from oleoresin capsicum, which is derived from hot peppers. The potency of this compound diminishes over time due to oxidation and other chemical processes. As it degrades, the spray becomes less effective, meaning it may not produce the intended effect of incapacitating an attacker.
2. Propellant Loss: Most pepper sprays use a propellant to eject the spray from its container. Over time, the propellant can leak, even if the container hasn't been used. This leakage reduces the pressure inside the canister, making the spray less effective or possibly rendering it unable to spray at all.
3. Seal Deterioration: The seals and moving parts of the spray mechanism can also degrade or become clogged over time. Rubber components may dry out, crack, or otherwise fail, leading to leaks or failure of the spray mechanism when the trigger is pressed.
4. Environmental Factors: Exposure to extreme temperatures, both hot and cold, can accelerate the degradation of both the pepper spray formula and its container. This makes it even more crucial to heed the expiration date, as storing the canister in environments like a car can significantly shorten its effective lifespan.

Manufacturers include an expiration date on pepper spray products to ensure users can rely on them for defense. Using a canister past its expiration could mean it doesn't work when you most need it, putting the user at risk. It's always recommended to test your pepper spray periodically (in a safe and controlled environment) and replace it by the expiration date or sooner if it's used.