If you have ever come across the concept of smell training, you most likely have noticed the recommendation of smelling fruity and spicy scents, especially 4 essential oils that are the most commonly recommended: fruity, spicy, floral, and eucalyptus. Below is a brief overview of how these specific scents were originally chosen and why they have become the top choice for smell training. How were the specific scents originally chosen? The book “Der Geruch” (Smell), written by the German psychologist Hans Henning in 1916, is a comprehensive discourse that attempts to understand and classify smells. Henning defined six main groups – floral, rotten, fruity, burnt, spicy, and eucalyptus – and created a ‘smell prism’ where each corner represents one of these scent groups in a person’s sense of smell. But how did this book by Henning pave the way for our 21st-century smell training with fruity, spicy, floral, and eucalyptus scents? To have patients avoid unpleasant and inconvenient experiences from smelling rotten and burnt scents, four remaining groups were chosen for smell training: fruity (lemon), spicy (clove), floral (rose), and resinous (eucalyptus). The 4 most recommended scents for smell training In 2009, Professor Thomas Hummel conducted a major research study at the University of Dresden. He came up with the most widely used smell training through his study, by intensively smelling rose, eucalyptus, lemon, and clove twice a day. This training, originally prescribed by ear, nose, and throat doctors all over the world, was developed as a therapy for people with loss of smell ever since. Experiment with other scents and endure unpleasant ones Although the classic four scents, first described by Professor Hummel in 2009, are mentioned most frequently in the literature, individuals can experiment with other scents. The golden rules of smell training include doing it consciously and not avoiding scents that may be perceived as disgusting through parosmia or hyposmia. Enduring the less pleasant scents seems to be an effective method to overcome the challenges of parosmia or hyposmia. Why fruity, spicy, floral, and eucalyptus scents? The recommendation to use fruity, spicy, floral, and eucalyptus scents when training the sense of smell depends on several factors. Fruity scents can include; citrus fruits (e.g. orange, lemon), berries (e.g. strawberry), peach, cherry, or melon. Spicy scents can include; vanilla, cinnamon, ginger, nutmeg, or cola. Floral scents can include; rose, jasmine, lavender, rosemary, or peony. Eucalyptus scents include; menthol and eucalyptus oil. Here are some reasons why these types of scents are often suggested: Diversity of smells: These categories encompass a wide range of distinct smells, providing a diverse set of olfactory stimuli. Training with a variety of scents helps enhance the ability to differentiate and recognize different odors. Intensity and Recognition: Floral, fruity, spicy, and eucalyptus scents tend to have clear and recognizable profiles, making them suitable for training. Their distinctive nature facilitates the learning and identification process during smell training. Positive Associations: Many floral and fruity scents are associated with positive and pleasant experiences. Using such scents can contribute to a more enjoyable and motivating smell training experience. Well-defined characteristics: Each category has well-defined characteristics. For instance, floral scents are often associated with flowers, fruity scents with various fruits, spicy scents with herbs and spices, and eucalyptus with a distinctive medicinal aroma. This clarity aids in the categorization and classification of different smells. Therapeutic Properties: Certain scents, such as eucalyptus, are known for their potential therapeutic properties, including respiratory benefits. This adds an extra dimension to smell training, potentially contributing to overall well-being. Conclusion It is important to note that there is not one “right” method for smell training, and different people may prefer various scents. Different smell training kits and programs may offer various scents and there is no universal standard for which scents should be used. Some training programs may also include neutral scents to increase the difficulty and versatility of the training. If you are considering starting smell training, it may be beneficial to use a set of scents designed specifically for smell training purposes. The goal is to expose the olfactory system to a variety of smells to enhance its sensitivity and discrimination abilities, especially in cases of hyposmia or parosmia (reduced or distorted sense of smell).