Ty Methylparaben, Broad Spectrum Preservative, 50g

Methylparaben is a chemical compound used as a preservative in many products, including cosmetics, food, and pharmaceuticals. It's also known as methyl 4-hydroxybenzoate. 
Methylparaben as an antimicrobial is effective against yeasts and molds.
It's also used in allergenic testing.
It's been used in amide anesthetic solutions to prevent contamination.
Methylparaben has a weak potential to cause allergies. 
It's associated with dermatitis, which can appear as a rash with itching, bumps, blisters, dry skin, swelling, tenderness, or burning, therefore, it should be used with caution. 
Methylparaben occurs naturally in a variety of plants, including blueberries.
Use at a minimum concentration of 0.2% and a maximum concentration of 0.4%. 

Methylparaben works very well against fungi, but less well against bacteria. In most cases, therefore, another preservative will be required, such as phenoxyethanol or other parabens, most commonly Propylparaben.