Purple Monkeyflower (Mimulus kelloggii or related Mimulus species) is primarily known in the context of flower essences, particularly in the Bach Flower Remedies tradition. Dr. Edward Bach, an English physician in the early 20th century, developed a system of flower remedies, attributing emotional healing properties to various flowers. The "Mimulus" remedy, which often includes Purple Monkeyflower or similar species, is recommended for individuals experiencing fear, particularly those with identifiable fears as opposed to vague anxieties.

The rationale for its use is based on Dr. Bach’s observations and holistic philosophy rather than clinical or scientific research. He believed that Mimulus flower essence could help individuals overcome excessive or everyday fears, such as fear of illness, pain, or public speaking. However, there is a lack of empirical scientific studies validating these claims. Most evidence remains anecdotal and rooted in long-standing tradition within the flower essence and homeopathy communities. Systematic reviews and clinical trials have not demonstrated efficacy for flower essences beyond placebo for psychological conditions, including fear or anxiety.

In summary, Purple Monkeyflower’s use for excessive fear is justified primarily by tradition, specifically within the Bach Flower Remedies approach, rather than by scientific evidence.