Why is it necessary to remove unreacted sodium hydroxide from the soap before using it on the skin?

Unreacted Sodium Hydroxide requires protected wearable like gloves, face mask, and eye protector before handling because it is a strong irritant and may harm the skin and eyes when came into contact. If ingested, it may affect the gastrointestinal system.That is why it is very important to remove, carefully, the sodium hydroxide in the soap.

Density and pressure