L. Gasseri is one of the species in BIFIDO|MAXIMUS, a Histamine-Free and D-Lactate Free Probiotic [20 Billion CFU of L. gasseri] which attempts to address two subsets of CFS patients. It is also available as a single species from Swanson [3 Billion CFU]. Neither indicated the strain(s).
“In humans, L. gasseri elicits various health benefits through its antimicrobial activity, bacteriocin production, and immunomodulation of the innate and adaptive systems. The genomic and empirical evidence supporting use of L. gasseri in probiotic applications is substantiated by clinical trial data displaying maintenance of vaginal homeostasis, mitigation of Helicobacter pylori infection, and amelioration of diarrhea.” 
Role in Pregnancy and New Borns
It appears to be one of the species that appears to be transfer to new borns and dominate the vagina during pregnancy. “L. crispatus, L. gasseri and/or L. jensenii were present… but as their estrogen levels rose, their flora composition altered, to become dominated by one of the three species most common in a normal, healthy vagina.”
- Lactobacillus gasseri OLL2809 is effective especially on the menstrual pain and dysmenorrhea in endometriosis patients: randomized, double-blind, placebo-controlled study .
- “L. rhamnosus and L. gasseri were the most common species in this period [in 6 months after birth].” 
Probiotic potential of 3 Lactobacilli strains isolated from breast milk. L.gasseri strains were two of these.
Allergy (i.e. Histamines)
- Orally administrated Lactobacillus gasseri TMC0356 and Lactobacillus GG alleviated nasal blockage of guinea pig with allergic rhinitis (2007).
- Lactobacillus gasseri suppresses Th17 pro-inflammatory response and attenuates allergen-induced airway inflammation in a mouse model of allergic asthma.
- Efficacy of oral administration of a heat-killed Lactobacillus gasseri OLL2809 on patients of Japanese cedar pollinosis with high Japanese-cedar pollen-specific IgE. “was found to be effective in reducing symptoms in subjects with a high predisposition to allergies by modulating systemic immune systems.”
- “Among the lactobacilli tested, L. gasseri OLL2809 showed the highest activity in reducing the level of antigen-specific IgE…is a good candidate for potential probiotics in terms of either the prevention or amelioration of allergic diseases or both.” 
- Oral administration of Lactobacillus gasseri SBT2055 is effective for preventing influenza in mice.
- Inhibition of Staphylococcus aureus by H2O2-producing Lactobacillus gasseri isolated from the vaginal tract of cattle.
- Probiotic (yogurt) containing Lactobacillus gasseri OLL2716 is effective for preventing Candida albicans-induced mucosal inflammation and proliferation in the forestomach of diabetic rats.
- Lactobacillus gasseri KS-13, Bifidobacterium bifidum G9-1, and Bifidobacterium longum MM-2 Ingestion Induces a Less Inflammatory Cytokine Profile and a Potentially Beneficial Shift in Gut Microbiota in Older Adults: A Randomized, Double-Blind, Placebo-Controlled, Crossover Study .
- Heat-killed Lactobacillus gasseri can enhance immunity in the elderly in a double-blind, placebo-controlled clinical study
Anti-obesity effect of Lactobacillus gasseri SBT2055 accompanied by inhibition of pro-inflammatory gene expression in the visceral adipose tissue in diet-induced obese mice.
- Effect of Lactobacillus gasseri BNR17 on Overweight and Obese Adults: A Randomized, Double-Blind Clinical Trial. “Despite there being no change in behavior or diet, administration of only the supplement of BNR17 reduced weight and waist and hip circumference.”
- Anti-obesity effect of Lactobacillus gasseri BNR17 in high-sucrose diet-induced obese mice .
- [Positive] Effects of heat-inactivated Lactobacillus gasseri TMC0356 on metabolic characteristics and immunity of rats with the metabolic syndrome .
- Gassericin A: a circular bacteriocin produced by lactic acid bacteria Lactobacillus gasseri . This is one of the antibiotics it produces. It is in the same family as the one produced by L.Reuteri.
- Yogurt containing Lactobacillus gasseri OLL 2716 (LG21 yogurt) accelerated the healing of acetic acid-induced gastric ulcer in rats.
- “Lactobacillus gasseri BNR17 has a suppressing effect on blood glucose levels and improved diabetic symptoms in db/db mice.” 
- Hypocholesterolemic effect of Lactobacillus gasseri SBT0270 in rats fed a cholesterol-enriched diet .
- “Adherent strains of bacteria such as Lactobacillus gasseri (ADH) on are likely to survive passage through the gastrointestinal tract and thus have greater metabolic effects.”
This lactibacillus species is definitely one that should be considered in the rotation of probiotics. Speculation: because of its involvement in female reproduction, females may be far more sensitive to it’s reduction than males, thus accounting for the difference of incidence between man and women.