This is an important detail that changes things significantly - 1 month of foul-smelling gas is a much longer, more chronic pattern than the 3-4 days of cramping/mucus you first mentioned. This points away from a simple short-term dietary upset and toward a malabsorption or bacterial overgrowth process.
Most likely explanations
1. Small Intestinal Bacterial Overgrowth (SIBO)
Bacteria that normally live in the large intestine overgrow in the small intestine and ferment food (especially carbs) before it's properly digested, producing excess, foul-smelling gas, bloating, and cramping - often worse after eating. Fits your combination of gas, cramping, and altered stool over a month.
2. Malabsorption (fat, carbohydrate, or general)
Medical textbooks describe a classic pattern: "abdominal distention, foul-smelling flatus... gas production from bacterial fermentation of carbohydrates in the colon, SIBO" and, for fat malabsorption specifically, "steatorrhea, foul-smelling flatus, weight loss" (Sleisenger and Fordtran's Gastrointestinal and Liver Disease). Malabsorption can come from:
- Lactose intolerance - undigested lactose ferments in the colon, producing gas and bloating
- Celiac disease - gluten-triggered malabsorption; foul gas after wheat/barley/rye is a classic clue
- Pancreatic insufficiency - reduced digestive enzymes, sometimes with pale/greasy stool
3. Giardiasis (parasitic infection)
A textbook describes giardiasis as causing "intermittent abdominal cramping and bloating, and almost intolerable foul-smelling flatus and stools," sometimes becoming chronic with weight loss if untreated. This is caught from contaminated water/food and can persist for weeks if not treated.
4. IBS
Can cause chronic gas and bloating, but foul odor specifically points more toward the fermentation/malabsorption causes above than classic IBS.
Why this now matters more
Combined with your earlier symptoms (mucus in stool, cramping, altered frequency), a full month of foul gas raises the likelihood of an underlying process like SIBO, lactose/carbohydrate malabsorption, giardiasis, or early celiac disease rather than a passing stomach bug. The digestive enzyme syrup (Aristozyme) is unlikely to resolve this - it may mask symptoms rather than address the cause.
What I'd recommend
- See a doctor - a month of foul-smelling gas plus cramping and mucus in stool warrants proper workup: stool exam (for parasites like Giardia), possibly a hydrogen/methane breath test (for SIBO or lactose intolerance), and if indicated, celiac serology (tTG-IgA)
- Track whether symptoms worsen after specific foods - dairy (lactose), wheat/bread (gluten), or high-FODMAP foods (onion, garlic, beans) - this alone can help narrow the cause
- Note any weight loss, fatigue, or pale/greasy stools and mention these to your doctor, as they suggest malabsorption
- Avoid self-treating for another month without an answer - persistent foul gas for this long is your body's signal that something specific needs identifying, not just symptomatic relief
Given the one-month duration, this has moved past the "wait and see with dietary changes" stage - a stool test and basic workup would be the sensible next step.