Is vitamin A excess toxic?

Yes. Hypervitaminosis A may develop either acutely or chronically. Acute toxicity is rare but is most commonly due to vitamin A overdose. It has also been documented in Arctic explorers consuming polar bear livers, which are rich in vitamin A. Clinically, it presents as large areas of desquamation associated with headache and vomiting. Chronic toxicity is more common and displays features associated with side effects of retinoid therapy: alopecia, exfoliation, and skin dryness. Pseudotumor cerebri with papilledema may occur early before any other signs. All symptoms and signs resolve in days to weeks following cessation of supplementation.