From Wikipedia, the free encyclopedia. Phototoxicity, also called photoirritation, is a chemically induced skin irritation, requiring light, that does not involve the immune system. It is a type of photosensitivity. The skin response resembles an exaggerated sunburn.
The contribution margin ratio is the difference between a company's sales and variable expenses, expressed as a percentage. The total margin generated by an entity represents the total earnings available to pay for fixed expenses and generate a profit.
The first variable you need to find for the contribution margin equation is its unit revenue â in other words, the price it's sold for. The confusing term unit revenue is used in economics because the product's price is equal to the revenue generated by the sale of a single product (or one unit).ontribution margin is a concept often used in a branch of managerial accounting known as cost-volume-profit (CVP) analysis. A single product's contribution margin is given with the formula P-V, where P is the cost of the product and V is its variable cost.