Water-based paints include water color, acrylic, gouache, tempera and casein.  Water is used for thinning and cleanup.

Hazards

• Acrylic paints contain a small amount of ammonia.  Some people who are sensitive may experience eye, nose and throat irritation from the ammonia.  Acrylics and some gouaches contain a very small amount of formaldehyde as a preservative.  People already sensitized to formaldehyde could experience allergic reactions from the trace amount of formaldehyde found in acrylics.  The amounts can vary from manufacturer to manufacturer.
• Casein paints use the protein casein as a binder.  While soluble forms are available, casein can be dissolved in ammonium hydroxide which is moderately irritating by skin contact and highly irritating by eye contact, ingestion, and inhalation.
• All water-based paints contain a preservative to prevent mold or bacterial growth. Although present in small amounts, some preservatives may cause allergic reactions in some people and not others.

Precautions

• Never add your own preservative. For tempera, a small amount of pine oil works for short periods of time.
• If you experience eye, nose or throat irritation while using acrylics, opening a window and increasing ventilation in the area in which you are working is usually sufficient.