The use of Bael (Aegle marmelos) for treating or supporting "blood poisoning" (a non-specific lay term often referring to sepsis or systemic infection) is rooted primarily in traditional medicine, especially within Ayurvedic and folk practices of India and Southeast Asia. In these systems, Bael fruit, root, and leaves have been used for their purported cleansing, antimicrobial, and anti-inflammatory properties. However, the specific use of Bael for "blood poisoning" is not strongly documented in traditional texts; rather, Bael is more commonly recommended for gastrointestinal ailments such as diarrhea, dysentery, and digestive issues.

From a scientific standpoint, there is limited evidence to support the effectiveness of Bael against systemic infections or sepsis. Some laboratory studies have shown that extracts from Bael possess antibacterial and antioxidant properties, but these findings are preliminary and do not directly translate to efficacy in treating severe bloodstream infections in humans. There are no high-quality clinical trials or pharmacological studies validating Bael’s use for this condition.

In summary, while Bael is valued in traditional medicine for various ailments, its application in "blood poisoning" is based on broader traditional beliefs in its purifying and antimicrobial effects rather than specific evidence or scientific validation. The evidence supporting its use for this particular condition is weak.