Persistent itching can be maddening, especially when you can't identify the cause. If you haven't switched to a new laundry detergent or soap lately, and if you have no other symptoms, you might consider that what you're ingesting is the source of the problem. Food allergies can cause itching, but some supplements can do so as well, particularly when taken in excess or in combination with certain foods or beverages.
Allergy to Your Multi
Although multivitamins are useful to treat or prevent vitamin deficiencies due to poor diet or certain illnesses, it's possible to have an allergic reaction to one or more of the ingredients in your multivitamin. Itchy skin may indicate an allergy, along with hives or a rash causing your skin to become red, swollen and blistered, warns Drugs.com. Other symptoms of an allergic reaction to multivitamins include swelling of the face, mouth, lips, tongue or throat. Get medical attention if you experience any of these side effects from taking a multivitamin.
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High Doses of Vitamin A
High doses of vitamin A might also be the culprit behind your itching. According to the Colorado State University Extension website, most American adults run no risk of being deficient in this vitamin, even without taking supplements. Many individuals take supplements, anyway. Some multivitamins include vitamin A in the form of beta-carotene, which won't cause an itching reaction. However, if your supplement doesn't specifically say how much, if any, of the vitamin A content is from beta-carotene, you might find yourself scratching, especially if you take upwards of 3,000 mcg over the course of a day. Some multivitamins contain a great deal of vitamin A, so if you additionally take another vitamin A supplement, you could reach this level.
Adverse Reactions from Niacin
Niacin, or vitamin B3, is somewhat notorious for causing adverse physical reactions in high doses. It's surprisingly easy to ingest too much of it without being aware. For example, energy drinks usually have a very high niacin content. If you use these drinks, and if you also take a multivitamin supplement that includes niacin, you can easily get too much. Your body doesn't need more than 17 mg a day, and some multivitamins include as much as 14 mg. Even one energy drink a day, in addition to a multivitamin, can put you well over 17 mg, and itchy skin can result.
Too Much Magnesium
Magnesium is an element found in many multivitamins, usually in doses of about 50 mg. Some laxatives and antacids also include it as magnesium oxide, because this form is relatively inexpensive to manufacture. You can also purchase magnesium as a single supplement without a prescription. If you double-up on sources, you might get too much. Itchy palms, feet and limbs can result, usually accompanied by a rash or hives. If this occurs, seek medical help, particularly if you also experience light-headedness, nausea or weakness. Take your antacid, laxative or vitamin supplements with you to show your physician exactly how much magnesium you've ingested.
Is this an emergency? If you are experiencing serious medical symptoms, please see the National Library of Medicine’s list of signs you need emergency medical attention or call 911.