OPALS® (Ogren Plant-Allergy Scale) is a science-based tool designed for improved, smarter, allergy and asthma-friendly plant selection. OPALS® has been used by many individuals worldwide, by allergy and asthma coalitions, by cities, schools, parks, hospitals, state departments of public health, by lung associations, and by the United States Department of Agriculture.
OPALS® uses a numerical scale to rank plants, ranging from 1 (least allergenic) to 10 (most allergenic). More than 130 different criteria are used to develop allergy rankings for plants. Each factor is either positive or negative. All factors are not weighted the same because some are more important than others. Most plants will have a combination of positive and negative factors that are computed to determine their OPALS® ranking.Some of the factors used to rank a plant are:
- The amount of pollen produced, if any
- Potency of the individual pollen grains
- The amount of time during a year that the plant is in bloom
- The size, density, shape, and weight of the pollen grains
- The dryness or stickiness of the grains
- Is the tree perfect flowered, monoecious, dioecious, or polygamous
- Sex of plant, if dioecious
- Position on the plant of pollen flowers
- Average rankings in actual skin scratch, patch, and sniff tests
- Cross-reactivity to food allergies
For more information, go to OPALS in Wikipedia.