Potential main modifiers of allergy markers according to population-based data
| Factors | Total IgE | SPT Positivity | Eosinophils | Comments |
| Genetics | ||||
| Genetic markers | + | + | + | Problematic for geneticists |
| Gender | + | + | ± | ↑ IgE for men |
| ↑ SPT for men | ||||
| Ethnic group | + | + | ± | ↑ IgE in some groups (genetic, environmental, social) |
| Individual susceptibility | + | + | ? | ↑ IgE, ↑ atopy |
| Family history of atopy | + | + | ? | |
| Individuals | ||||
| Maternal age at birth | + | ? | ? | ↓ IgE in newborns of young mothers |
| Perinatal complications | ± | ? | ? | ↑ IgE in newborns |
| Medication during pregnancy | + | ? | ? | ↑ IgE in newborns (progesterone) |
| Head circumference | ± | ? | ↑ IgE in adults and newborns if head circumference at birth ≥37 cm | |
| Birth weight | ± | ? | - | ↓ IgE in low birth weight |
| Birth month | + | ? | - | ↑ IgE during pollen season |
| Age | + | + | + | Increase in youth and decrease with age |
| Infections | ± | ± | - | Depend on age of infection |
| Family size | - | + | - | Depends also on birth order |
| Environmental | ||||
| Maternal smoking during pregnancy | ± | ? | ? | Contradictory results for IgE |
| Active smoking | + | Inversely related | + | ↑ IgE with active smoking ↑ eosinophils |
| Passive smoking | ± | ± | ± | Among children |
| Allergens exposure | + | + | - | |
| Month of test | ± | ? | - | ↑ IgE during pollen season |
| Indoor pollution (humidity, mite) | ± | ± | ? | ↑ IgE mites |
| Outdoor pollution (NO2, SO2, diesel) | ± | ± | ? | ↑ IgE with diesel |
| Occupational exposure | + | + | ? | ↑ IgE in individuals exposed to allergens, dust, gas and fumes |
?: No evidence, investigation is required; ±: uncertain relationship; +: established relationship; -: not yet studied in population-based samples; ↑: increase; ↓: decrease; SPT: skin prick test; NO2: nitrogen dioxide; IgE: immunoglobulin E.