- Onion oil is a popular hair care product because of its many benefits for hair growth. Here are some of the key points to remember about onion oil for hair health: - Onion oil is a natural conditioner that is safe for use during pregnancy. It helps to control hair fall and regrowth, and has been popular in recent years for its deeply embedded ayurvedic practices and Dominican culture. - Onion oil is also used as a carrier oil in hair products, and is especially beneficial for hair growth because it has anti-fungal, anti-bacterial, and anti-inflammatory properties. - One of the most popular ways to apply onion oil to the scalp is by using onion juice. This method has been touted by musician Cardi B as a secret to healthy hair, with noticeable results after just two washes.