Allergies
Everything in the library studied for it, medical and holistic together. Within each kind, what was shown to help comes first, strongest evidence first. What was tested and not shown to help stays on the list.
Strong several reviews agree · Moderate one review or consistent trials · Limited one or a few small studies · Untested no study in people, listed with what it rests on
Medication
Hay fever and other allergic rhinitis
Shown to lower hay fever symptom scores more than placebo, but nasal steroid sprays relieved nasal symptoms more than oral antihistamines.
Compared with placebo [1][2]; nasal corticosteroid sprays [3]
The numbers and sources
- Effect
- In a perennial allergic rhinitis trial, levocetirizine 5 mg lowered the 4-symptom total score (0 to 12) by 1.22 points more than placebo (95% CI 0.76 to 1.69), with similar results at 2.5 and 10 mg [1]. A network meta-analysis found six of seven total nasal symptom estimates in seasonal rhinitis favored active treatment over placebo, but rated all comparisons between drugs very low certainty and found no reliable ranking [2]. Against oral antihistamines, nasal steroids gave more relief of total nasal symptoms (SMD -0.42), blockage (SMD -0.63) and sneezing, with no difference for eye symptoms [3].
- Population
- 517 people aged 12 and older in one levocetirizine trial [1]; 34,831 participants in 61 reports [2]; randomized trials comparing nasal steroids with oral antihistamines [3].
- Sources
- [1], [2], [3]
- Caveats
- The network meta-analysis found the evidence mostly placebo-anchored and sparse [2]. The nasal steroid comparison dates from 1998 [3].
Chronic hives
Shown to clear chronic hives completely more often than placebo, about 2.7 times as often with cetirizine 10 mg, in evidence drawn from few studies.
Compared with placebo [4][1]; other antihistamines [4]
The numbers and sources
- Effect
- Cetirizine 10 mg once daily led to complete suppression of urticaria more often than placebo (RR 2.72, 95% CI 1.51 to 4.91). Levocetirizine 5 mg beat placebo in the intermediate term but not the short term, and desloratadine results had very wide intervals. More people had complete suppression on cetirizine than on fexofenadine. Withdrawals for adverse events did not differ significantly [4]. In two 4-week label trials, levocetirizine 2.5, 5 and 10 mg lowered itch scores more than placebo, with fewer and smaller wheals [1].
- Population
- 9,759 participants in 73 studies [4]; 423 adults aged 18 to 85 with chronic idiopathic urticaria [1].
- Sources
- [4], [1]
- Caveats
- Most comparisons rest on few studies or single-study estimates [4].
Hay fever (seasonal allergic rhinitis)
Shown to improve hay fever symptoms modestly against placebo, about 5% more, slightly less than antihistamines and less than nasal steroid sprays.
Compared with placebo [5]; antihistamines [5]; nasal corticosteroids [5]
The numbers and sources
- Effect
- Leukotriene receptor antagonists lowered daily rhinitis symptom scores 5% (95% CI 3% to 7%) more than placebo and improved rhinoconjunctivitis quality of life by 0.3 units. Antihistamines improved nasal symptoms 2% (95% CI 0% to 4%) more, and nasal corticosteroids 12% (95% CI 5% to 18%) more, than leukotriene receptor antagonists [5].
- Population
- 8 trials with 3,924 people with seasonal allergic rhinitis [5].
- Sources
- [5]
- Caveats
- No randomized trials of perennial rhinitis were found in this review [5]. The label reserves rhinitis use for people who did not respond to or could not take other treatments [1].
Hives, added to an antihistamine
Small trials found adding ranitidine or cimetidine to diphenhydramine cleared hives more often than diphenhydramine alone. The evidence was old and at high or unclear risk of bias.
Compared with diphenhydramine alone [8]
The numbers and sources
- Effect
- Ranitidine with diphenhydramine resolved urticaria more often than diphenhydramine alone (RR 1.59, 95% CI 1.07 to 2.36). Cimetidine alone did not improve overall symptoms more than diphenhydramine, but the combination did (RR 2.02, 95% CI 1.03 to 3.94). Sedation from baseline did not differ with famotidine or diphenhydramine [8].
- Population
- 144 participants in 4 small studies [8].
- Sources
- [8]
- Caveats
- The review authors called the evidence very limited and rated the studies at high to unclear risk of bias. The direct evidence is for ranitidine and cimetidine, not famotidine [8].
Itching
Limited evidence: hydroxyzine matched loratadine for clearing chronic hives in one comparison, and itch scores fell in a small dialysis trial with no placebo group.
The numbers and sources
- Effect
- In a Cochrane review of antihistamines for chronic hives, complete suppression over the short term did not differ between hydroxyzine 25 mg and loratadine 10 mg (RR 1.00, 95% CI 0.32 to 3.10) [8]. In a crossover trial in people on dialysis, itch severity on a 10-point scale fell from 6.83 to 2.86 over 6 weeks on hydroxyzine 25 mg a day and from 7.1 to 2.17 on gabapentin, with no significant difference between the two [9]. A Cochrane review found no randomized trial of an oral antihistamine used alone for eczema [10].
- Population
- 73 studies of antihistamines with 9,759 participants, of which one comparison involved hydroxyzine [8]; 32 patients on dialysis [9].
- Sources
- [8], [9], [10]
- Caveats
- An approved use that rests on older evidence. Neither comparison here had a placebo arm for hydroxyzine, and the hives comparison had a wide confidence interval.
Higher doses for hives that do not respond
Mixed results: raising the dose of a non-sedating antihistamine improved itch in chronic hives but did not change response rates or the number of wheals.
Compared with standard doses and placebo [5]
The numbers and sources
- Effect
- Response rates and wheal counts did not differ between standard and higher doses. Higher doses significantly improved the itch score of the Urticaria Activity Score [5].
- Population
- 15 studies of chronic spontaneous urticaria [5].
- Sources
- [5]
- Caveats
- Only five studies were of high quality, and heterogeneity was significant [5].
Chronic hives
Limited evidence: most trials found leukotriene blockers alone no better than placebo or antihistamines for chronic hives, while adding one to an antihistamine appeared to help more.
Compared with placebo or antihistamines [6]
The numbers and sources
- Effect
- Across 10 randomized trials, most found leukotriene receptor antagonists not superior to placebo or antihistamines as monotherapy, while the combination with antihistamines appeared to improve hives more than antihistamines alone. Heterogeneity was too high for a pooled analysis [6].
- Population
- 10 randomized or crossover trials in chronic urticaria [6].
- Sources
- [6]
- Caveats
- No pooled estimate. Trials differed in design and outcomes [6].
Anaphylaxis
Not studied in people. A Cochrane review found no randomized trial of H1 antihistamines for anaphylaxis, a use that rests on how they block histamine.
No study in people. This rests on how it acts in the body.
The numbers and sources
- Effect
- A Cochrane review searched for randomized and quasi-randomized trials of H1 antihistamines for anaphylaxis with or without shock and found none that met its criteria. The authors stated they could not draw conclusions for practice [11].
- Population
- No trials located [11].
- Sources
- [11]
- Caveats
- Antihistamines block histamine, one of several mediators of anaphylaxis. Without trials, any effect on outcomes such as survival is unknown [11].
Supplements
Seasonal allergies
Small uncontrolled trials found fewer nasal allergy symptoms after 2 to 4 weeks of MSM, measured against each person's own baseline.
Compared with before MSM, in the same people [8][9]
The numbers and sources
- Effect
- In an open-label trial, 50 people with seasonal allergic rhinitis took 2,600 mg a day for 30 days, and upper and total respiratory symptoms fell significantly from baseline by day 7 [8]. In a randomized, double-blind study comparing doses after a standard allergen challenge, 1, 3 or 6 g a day for 14 days lowered average nasal symptom scores 53.72% from baseline (P = .001) and raised nasal airflow 17.32% (P = .02). No adverse events occurred [9].
- Population
- 50 adults with seasonal allergic rhinitis, 30 days [8]. Adults with a history of allergic nasal congestion, 14 days [9].
- Sources
- [8], [9]
- Caveats
- Neither study had a placebo group. The second study randomized people between doses, not to placebo, and its abstract does not give the number enrolled [9]. The first trial's abstract does not give the size of the fall [8].
Therapies
Allergic rhinitis
Shown to lower nasal symptom scores in pooled trials. The largest trial found small gains over sham acupuncture that its authors said may not be clinically meaningful.
Compared with control groups the source abstract does not describe [13]; sham acupuncture [14]; rescue antihistamine alone [14]
The numbers and sources
- Effect
- Across 13 trials, nasal symptom scores fell more with acupuncture than with control (weighted mean difference -4.42, 95% CI -8.42 to -0.43) and medication scores fell too [13]. In 422 people with seasonal allergic rhinitis, 12 sessions improved rhinitis quality of life by 0.5 points more than sham acupuncture and 0.7 points more than antihistamine alone after 8 weeks. The differences were gone by week 16 [14].
- Population
- 2,365 participants in 13 trials [13]. 422 adults sensitized to birch and grass pollen in Germany [14].
- Sources
- [13], [14]
- Caveats
- The meta-analysis abstract does not say what its control groups received [13]. Baseline scores in the largest trial were low [14].
Hay fever, allergies and allergic asthma
Mixed results: early small trials found less nasal blockage than placebo, and later trials in allergic asthma and hay fever found no difference.
Compared with placebo [5][12][13][14]
The numbers and sources
- Effect
- In an early pooled analysis, four trials of one remedy for seasonal allergies favored homeopathy for eye symptoms at 4 weeks (OR 2.03, 95% CI 1.51 to 2.74) [5]. In 51 people with perennial allergic rhinitis, a 30c dilution of their main allergen improved nasal airflow by 19.8 L/min more than placebo (95% CI 10.4 to 29.1), and symptom scores did not differ [12]. In 242 people with asthma allergic to house dust mite, homeopathic immunotherapy did not differ from placebo on most outcomes over 16 weeks [13]. In 62 people with seasonal allergic rhinitis, neither a standard nor an individualized remedy improved quality of life more than placebo [14].
- Population
- 4 trials [5]. 51 adults in Scotland [12]. 242 adults in 38 English general practices [13]. 62 adults in Germany [14].
- Sources
- [5], [12], [13], [14]
- Caveats
- The 2026 trial reached about a quarter of its planned size [14]. The 51-person trial was run by the group whose three earlier trials it added to [12].
Daily life
Eczema in children
Linked to about 28% less eczema in children exposed to dogs in one meta-analysis of birth cohorts. Cat exposure was not linked.
Compared with children not exposed to dogs, cats or pets [12]
The numbers and sources
- Effect
- Exposure to dogs (RR 0.72, 95% CI 0.61 to 0.85) and to pets overall (RR 0.75, 95% CI 0.67 to 0.85) was linked to less atopic dermatitis. Exposure to cats was not (RR 0.94, 95% CI 0.76 to 1.16) [12].
- Population
- Children in 21 birth cohorts, 26 publications, exposed during pregnancy, infancy or childhood [12].
- Sources
- [12]
- Caveats
- Observational. Families with allergies may avoid getting pets, which can make pets look protective. Heterogeneity was moderate (I² 46% for dogs) [12].
Food and drink
Peanut allergy in high-risk infants
One trial in infants at high risk found peanut allergy at age 5 in 1.9% of those fed peanut and 13.7% of those who avoided it.
Compared with avoiding peanut until 60 months of age [14]
The numbers and sources
- Effect
- In infants with a negative skin test at the start, peanut allergy at 60 months was 13.7% with avoidance and 1.9% with regular peanut consumption (P < 0.001). In infants with a small positive skin test, it was 35.3% and 10.6% (P = 0.004). Serious adverse events did not differ significantly between groups [14]. The FDA lists a qualified health claim for ground peanuts and reduced risk of developing peanut allergy [2].
- Population
- 640 infants aged 4 to 11 months with severe eczema, egg allergy or both [14].
- Sources
- [14], [2]
- Caveats
- One trial in infants at high risk. It does not test nuts in older children or adults.