Although uncommon, certain individuals who are sensitive to iodine can develop acne breakouts, rashes, or other skin reactions when consuming iodine from iodized table salt (specialty salts such as Himalayan salt are typically not iodized) or supplements such as certain multivitamins and kelp supplements. For more about this, and other potential side effects and drug interactions with iodine-containing supplements, see the Concerns and Cautions section of the Kelp Supplements Review.
People who are sensitive to iodine should be aware that iodine may be present in products that you may not expect, including certain protein powders and shakes, nutrition bars, meal replacement powders and shakes, greens and whole foods supplements, and even some probiotic supplements and menopause products.
Iodine is essential for healthy functioning of the thyroid gland which, among other things, controls the body's metabolism, and, during pregnancy and infancy, influences bone and brain development.
Be aware that taking very large doses of vitamin B12 can cause outbreaks of acne -- even in older people.