The name of vitamin A designates the group of retinoids, i.e., some
lipophilic substances, which include carotenoids, retinol, retinal and retinoic acid and
their synthetic derivatives. Carotenoids and retinoids have several similar biological
activities such as antioxidant properties, beneficial effects on the skin, the inhibition of
malignant tumor growth and the induction of apoptosis. Retinoic acid [RA] is the
active form of the retinol isoform of vitamin A, while retinol is its vitamer form found
in food and is converted in the body to 11-trans-retinal by an oxidative process where
the hydroxyl group is converted into an aldehyde. 11-trans-retinal is subsequently
isomerized into 11-cis-retinal, the functional isomer of the vitamin important in the
physiology of vision. Among carotenoids, beta carotene is the pro-vitamin A form
obtained from vegetables. Hypervitaminosis A and the relative toxicity usually occur as
a consequence of the administration of large amounts of vitamin A preparations,
usually for therapeutic purposes. Many esters of vitamin A have been isolated and
produced and following their topical use in cosmetics, allergic contact dermatitis has
been reported. Furthermore, from retinoic acid, a new class of drugs largely used in
dermatology have been produced and the first representant was the cis-retinoic acid or
isotretinoin and many others which can be assumed orally to treat severe acne. Such
drugs have induced contact dermatitis, photodermatitis, but also urticaria/angioedema
with a pseudoallergic mechanism due to the imbalance of inflammatory prostaglandins.
On the contrary, true allergic reactions like anaphylaxis from these vitamin A
derivative drugs are attributed to their emulsifier, the soybean oil, able to induce severe
reactions in peanut allergic patients.
Keywords: Allergic Contact Dermatitis, Anaphylaxis, Angioedema, Beta-
Carotene, Food Allergy, Food Dyes, Isotretinoin, Patch Tests, Peanut, Pro-vitamin
A, Retinoic Acid, Retinoids, Retinol, Retinyl Acetate, Retinyl Palmitate, Skin
Tests, Soybean, Tretinoin, Urticaria, Vitamin A.
