Irritation can also be reduced by avoiding harsh facial cleansers and wearing sunscreen prior to sun exposure.One in 500 people experience hypersensitivity to BPO and are liable to experience burning, itching, crusting, and possibly swelling. About one-third of people experience phototoxicity under exposure to ultraviolet (UVB) light. Dosage
In the U.S., the typical concentration for benzoyl peroxide is 2.5% to 10% for both prescription and over-the-counter drug preparations that are used in treatment for acne. Other medical uses
Benzoyl peroxide is used in dentistry as a tooth whitening product. Non-medical uses
Bleaching
Like most peroxides, it is a powerful bleaching agent. It has been used for the bleaching of flour, fats, oils, waxes, and cheeses, as well as a stain remover. Polymerization
Benzoyl peroxide is also used as a radical initiator to induce chain-growth polymerization reactions, such as for polyester and poly(methyl methacrylate) (PMMA) resins and dental cements and restoratives. It is the most important among the various organic peroxides used for this purpose, a relatively safe alternative to the much more hazardous methyl ethyl ketone peroxide. It is also used in rubber curing and as a finishing agent for some acetate yarns. Safety
Explosion hazard
Concentrated benzoyl peroxide is potentially explosive like other organic peroxides, and can cause fires without external ignition. The hazard is acute for the pure material, so the compound is generally used as a solution or a paste. For example, cosmetics contain only a small percentage of benzoyl peroxide and pose no explosion risk.
Historically cyanide has been used for mass suicide and by the Nazis for genocide. Signs and symptoms
Acute exposure
If hydrogen cyanide is inhaled it can cause a coma with seizures, apnea, and cardiac arrest, with death following in a matter of seconds. At lower doses, loss of consciousness may be preceded by general weakness, dizziness, headaches, vertigo, confusion, and perceived difficulty in breathing. At the first stages of unconsciousness, breathing is often sufficient or even rapid, although the state of the person progresses towards a deep coma, sometimes accompanied by pulmonary edema, and finally cardiac arrest. A cherry red skin color that darkens may be present as the result of increased venous hemoglobin oxygen saturation. Despite the similar name, cyanide does not directly cause cyanosis. A fatal dose for humans can be as low as 1.5 mg/kg body weight. Other sources claim a lethal dose is 1–3 mg per kg body weight for vertebrates. Chronic exposure
Exposure to lower levels of cyanide over a long period (e.g., after use of improperly processed cassava roots, which are a primary food source in tropical Africa) results in increased blood cyanide levels, which can result in weakness and a variety of symptoms, including permanent paralysis, nervous lesions, hypothyroidism, and miscarriages. Other effects include mild liver and kidney damage. Causes
Cyanide poisoning can result from the ingestion of cyanide salts; imbibing pure liquid prussic acid; skin absorption of prussic acid; intravenous infusion of nitroprusside for hypertensive crisis; or the inhalation of hydrogen cyanide gas.