Freckles of the face and arms are always caused by exposure to sunlight. They arise from an increase in the coloring matter of the skin , and the best treatment is preventive treatment of protecting the face and arms from excessive exposure to the sun.
Lemon juice is a good and safe bleach for the skin , but I have not seen it have any effect on a areal crop of freckles. Strong peeling preparations should not be used , and will probably be useless on a thickly freckled skin, because the pigment is located deep in the skin.
Using strong chemical applications on the skin may it self cause pigmentation pigmentation of the skin. Freckling of th the skin in certain parts not exposed to sunlight may be a consequence of liver and gallbladder disease.
In pregnancy, brown blotches often appear on the nose , checks and neck, but they usually disappear after delivery. There is a skin disease called "vitiligo," which causes loss of pigment in parts of the skin so that the normal parts look dark by comparison.
But this is also an incurable condition. Bronzing of the skin from Addison's disease of the adrenal glands and jaundice from obstruction of the bile passages are conditions which require the close attention of a physician