Using baking soda to clean a memory foam pillow is a great home remedy, especially if your pillow has developed an unpleasant odor or dampness from prolonged use.
You can sprinkle baking soda on it, but you absolutely cannot leave it there permanently. Here's a detailed explanation of how to do it correctly and why:

⇒ Why sprinkle baking soda on a memory foam pillow?

Odor-absorbing "miracle":

Baking soda is a natural deodorizer that neutralizes odors caused by sweat and skin oils.

Moisture absorption:

Memory foam tends to retain heat and moisture, and baking soda can draw out some of the moisture from the pillow's surface.

⇒ Correct procedure

Evenly sprinkle:

Remove the outer pillowcase and lay the memory foam pillow flat on a bed or table. Sprinkle a thin, even layer of baking soda powder over the surface of the pillow core.

Let it sit:

Let it sit undisturbed for at least 30 minutes to 1 hour. If the odor is strong, leaving it for half a day is also fine. During this time, the baking soda will gradually absorb the odors.

Thoroughly vacuum:

This is the most crucial step! After the time is up, you must use a vacuum cleaner with a fabric brush attachment to thoroughly vacuum all the powder from the surface of the memory foam pillow.

⇒ Why can't you leave the baking soda in the pillow?

Although baking soda is non-toxic and harmless, if you don't vacuum it up completely before putting the pillowcase back on and sleeping on it, you will encounter the following problems:

Uncomfortable grainy texture:

Memory foam is known for its delicate, conforming feel. If there are fine powder particles remaining inside, it will feel gritty or like sleeping on sand.

Powder entering pores:

Your head and face are in close contact with the pillow for several hours every day. If the powder from the memory foam pillow gets out, it may clog your skin pores or even dry out your skin.

Soiling the inside of the pillow:

Memory foam has many tiny air pores. If the powder remains inside for a long time without being cleaned, combined with the moisture from body sweat, the powder may clump together, blocking the ventilation holes and making your memory foam pillow less and less breathable.