Sleeping with your phone under the pillow is a fire risk, not a cancer risk

Sleeping with a charging phone under your pillow is unlikely to give you cancer, but it can overheat. The old warning about radiation is overblown. The real concern is heat that has nowhere to go, which can wear out the battery and, in rare cases, start a fire.

What the research says

Cell phones give off non-ionizing radiofrequency radiation. That is a low-energy form of radiation. It does not carry enough strength to damage DNA the way X-rays or gamma rays can.

A 2024 systematic review, published in the journal Environment International, found moderate-certainty evidence that phone radiation likely does not raise the risk of several tumor types in adults. These include glioma, meningioma, acoustic neuroma, pituitary tumors and salivary gland tumors. It also found no likely link to brain tumors in children. The study was commissioned by the World Health Organization.

Why a pillow is the problem

Most smartphones use lithium-ion batteries. These batteries give off heat as they take in power. That heat needs a hard, open surface to escape safely. A pillow or blanket blocks the airflow, so the heat builds up.

Doing this a few times is not likely to cause trouble. Doing it again and again can.

• The battery wears out faster, because long heat exposure breaks down battery cells.
• Parts inside the phone can warp, or the phone can shut itself off for safety.
• Repeated overheating raises the odds of permanent hardware problems.

In rare cases, trapped heat and a damaged battery can lead to thermal runaway. That means the phone makes heat faster than it can shed it. At that point, a fire is a high risk. An uncertified charger makes overheating more likely, because it may lack proper heat control and surge protection.

What to do

The fix is simple. Charge your phone on a hard, flat, well-ventilated surface, such as a bedside table or desk. A hard floor next to the bed also works better than a pillow.

• Use a wireless charging pad on the nightstand as a set spot for the phone.
• Use only certified chargers.
• Try a classic alarm clock so the phone does not end up near your head.

You can still use your phone before bed and charge it overnight. It just needs room to breathe.