The phrase "make hair stand on end" refers to something that is frightening or unsettling. However, there are antonyms to this phrase that describe feelings of calm and reassurance. Some examples of these antonyms are: soothing, comforting, relaxing, pacifying, alleviating, relieving, and calming.
When we feel soothed or comforted, our body feels relaxed and at peace. This can be achieved through activities such as taking a warm bath or listening to relaxing music. Similarly, when we feel pacified or relieved, our mind becomes less anxious and more at ease.
Therefore, instead of trying to make someone's hair stand on end, we should strive to bring them a sense of calm and reassurance. This can be achieved through various means, such as practicing mindfulness or offering words of encouragement.