Summer evenings on the patio are one of life’s simple pleasures — until the mosquitoes show up. While commercial yard sprays and citronella candles have their place, a surprisingly popular folk remedy has been circulating among gardeners and backyard entertainers for years: a three-ingredient area spray made from blue mouthwash, stale beer, and Epsom salts. It’s cheap, easy to mix, and requires nothing more than a trip to the dollar store and a garden sprayer.

This is an area treatment, meant to be applied to grass, shrubs, patio furniture, and the perimeter of your outdoor seating space — not directly on skin. For on-body protection, stick with an EPA-registered repellent containing DEET, picaridin, or oil of lemon eucalyptus.

Ingredients

Ingredient Amount
Blue mint mouthwash (e.g., original blue Listerine) 3 cups
Stale beer (any inexpensive variety) 3 cups
Epsom salt 3 cups

The 1:1:1 ratio makes this easy to scale. Double or triple the batch for larger yards.

Instructions

  1. Combine the mouthwash, beer, and Epsom salt in a large bucket or bowl. Stir well until the salt is fully dissolved.
  2. Transfer the mixture to a hose-end garden sprayer or a large pump sprayer.
  3. Apply liberally around your yard, patio, deck, or outdoor seating area — covering grass, shrubs, and furniture surfaces.
  4. Reapply after rain or every few days as needed throughout the season.

Notes

  • A hose-end sprayer is the most convenient option for covering a full backyard quickly before a cookout or gathering.
  • The beer does not need to be fresh — flat or stale beer is perfectly fine, making this a good use for forgotten cans at the back of the fridge.
  • Scale up freely. The 1:1:1 ratio holds at any volume, so mix as much as your sprayer or storage container can hold.

Anecdotal Background

This recipe has spread widely through gardening forums, Facebook groups, and word of mouth — the kind of practical folk knowledge that passes from neighbor to neighbor before anyone thinks to look it up. Many people report noticeably fewer mosquitoes after treating their yards, particularly around standing vegetation and shaded areas where mosquitoes tend to rest during the day.

The working theory behind it is loosely grounded in the ingredients themselves:

  • Blue Listerine contains eucalyptol, menthol, thymol, and methyl salicylate — aromatic compounds that are also found in some commercially formulated insect repellents. Eucalyptol in particular has documented insect-repelling properties.
  • Beer (especially flat or fermented beer) is thought to add a fermented scent that may mask the carbon dioxide and lactic acid cues that attract mosquitoes to humans — though this mechanism is speculative.
  • Epsom salt (magnesium sulfate) is often included in garden spray recipes as a carrier or adjuvant. Some proponents suggest it helps the spray adhere to plant surfaces longer, extending residual effect.

It’s worth being clear: this recipe has not been scientifically validated as a mosquito repellent. There are no peer-reviewed studies confirming its efficacy, and results vary widely based on mosquito species, environmental conditions, and yard layout. That said, the ingredients are inexpensive and harmless to most plants and grass in typical concentrations, so the barrier to trying it is low.

Think of it as a reasonable supplement to other control strategies — eliminating standing water, keeping grass trimmed, and using personal repellent when you’re outside for extended periods. Many people find it a satisfying and low-cost addition to their summer pest management routine, even if the science behind it remains largely in the realm of backyard wisdom.