Weed, insect, and disease control may also be required for pastures. A healthy, productive pasture will resist invasion from most poisonous weeds and provide good quality forage. When pastures are overgrazed, horses will eat the grass and legume species down to the soil, which allows weeds to take over.
1 Melasma can be triggered by birth control pills because it increases hormones throughout the body. # 2  This is one of the most common causes of melasma. 3  Pregnancy: During pregnancy the body will become very hormonal and skin conditions like acne vulgaris and melasma/chloasma become very common.
Below the age of 20, acne can cause dark spots due to scarring and red marks left by the infection. Skin Diseases That Cause Dark Spots Melasma: Itâs one of the commonest causes of grayish patches on the face. It mostly affects the forehead, cheeks, or the area between your mouth and nose.