Kerassentials Side Effects and Safety: What to Know Before You Apply It

By Leah CorbinEditor, Kerassentials ReviewUpdated October 21, 20264 min read

Kerassentials goes on the outside of the body, which makes it a lower-risk choice than oral antifungal pills. Most people use it without any trouble. The things worth knowing are skin sensitivity to essential oils, the nut oils in the base, and a few situations where home treatment isn't the right first step.

The short answer

Side effects from Kerassentials are uncommon and mild. The most likely one is skin irritation (redness, stinging or itching) where the oil touches the skin around the nail, usually from the essential oils. The menthol and camphor give a cool tingle that is normal and fades in a few minutes.

The label's cautions are clear: external use only, keep it away from the eyes, don't swallow it, stop if irritation occurs and don't apply more than directed. If it is swallowed, drink water and get medical help right away.

Ingredients that can cause a reaction

Tea tree oil allergy is the best documented. Case reports of contact dermatitis go back decades, and the NCCIH notes that it can cause skin irritation and allergic reactions in some people. Old, oxidized tea tree oil is more likely to irritate, which is one reason to keep the cap tight and the bottle out of the sun.

How to patch test

Before your first full application, put a small drop on the inside of your forearm or on the skin next to one toe. Leave it for 24 hours. If you get redness, swelling, blisters or itching that lasts, don't use it. If the skin looks normal, start the full routine, and keep an eye on the skin around the nails for the first week.

Why it must never be swallowed

Several ingredients are toxic by mouth even in small amounts. Tea tree oil swallowed by children has caused confusion, loss of coordination and coma, and camphor is a well-known cause of poisoning in young children. Store the bottle where kids and pets can't reach it, close the cap after every use, and call Poison Control (1-800-222-1222 in the US) if anyone swallows it.

Pregnancy and children

The label doesn't give separate advice for pregnancy. Camphor and some essential oils are usually avoided in pregnancy and on young children's skin, so ask your doctor first if either applies. Children with nail changes should see a pediatrician or dermatologist anyway, since other conditions can look like fungus.

When to see a doctor instead

A nail oil is a reasonable first step for mild cases on one or a few nails. See a doctor or podiatrist first if:

• You have diabetes, poor circulation or nerve damage in your feet. The NIDDK advises people with diabetes to have foot problems checked rather than treated at home.
• The skin around the nail is red, hot, swollen or draining pus. That points to a bacterial infection.
• The nail is painful, lifting off, or has a dark streak, which needs a diagnosis.
• Most of the nail or many nails are affected. Oral prescription drugs clear more severe cases.
• You have a weakened immune system.

The AAD's nail fungus treatment guide explains what a dermatologist can offer, from prescription topicals to oral medicines.

Kerassentials compared with oral antifungals

Oral antifungal drugs such as terbinafine clear more infections than any topical, but they come with their own risks, including liver effects and drug interactions, which is why doctors order blood tests while you take them. A topical oil avoids that entirely. The trade-off is that topical treatments take longer and work best on milder cases. For many people with one or two lightly affected nails, starting with a topical makes sense.

Bottom line on safety

For a healthy adult with no nut allergy, Kerassentials is a low-risk product to try. Patch test first, apply it only to the nails and the skin right around them, keep it away from your eyes and out of reach of children, and stop if your skin reacts. You are still covered by the 60-day refund if it doesn't suit you.

For the full verdict, see the Kerassentials review. For what each ingredient does, see the ingredients page.

Signs of an allergic reaction

Stop using it and wash the area with soap and water if you notice spreading redness, swelling, small blisters, or itching that gets worse over a day or two. These are signs of contact dermatitis rather than the normal brief tingle. Mild reactions usually settle within a few days after stopping. See a doctor if the rash spreads, the skin cracks or weeps, or you have any swelling of the face or trouble breathing, which needs emergency care.

Most people who react do so in the first few days, so the first week is the time to watch the skin closely. If you get through it with no redness, problems later on are unlikely, though the skin can still react if it becomes cracked or broken.

Side effect questions