This is actually a tougher question to answer than you might think as we need to look at each of the claims (i.e. treatment of constipation, tummy aches, fevers and immunity) individually. I've tried to check to see what the most common treatment recommendations are by alternative medicine practitioners so that we aren't just randomly coming up with treatments.
First, we must remind ourselves exactly what an essential oil is:
An essential oil is a concentrated hydrophobic liquid containing
volatile aroma compounds from plants.
So with that in mind, I'm going to write this from the standpoint that a naturally produced essential oil may contain some difference that a synthetic fragrance oil may or may not have due to the chemistry of the oil.
Interestingly, searching seems to imply that there are several different oils that are recommended for use (1, 2, 3) and a common means of application for all of them, namely:
Application should be twice a day, once in the evening and then first
thing in the morning. Each session should last 5 to 7 minutes.
Massage should follow the direction of peristalsis following the
movement of food - clockwise start and the lower right part of the
lower abdomen where the appendix might me and up the ascending colon,
across the transverse colon and down the descending colon ending at
the top of the pubis.
This is very interesting as massage is actually mentioned as an alternative treatment by the Mayo Clinic and following up on this I find that it appears that massage in and of itself may be effective at reliving the symptoms of constipation. If this is the case than it is highly possible that the essential oils themselves have no effect but the means of applying them might be the actual cause of the relief of symptoms.
"Tummy aches", or stomach aches, or the much more generic abdominal pain is quite broad and turning to the Mayo Clinic again we get this list of potential causes:
- Stomach "flu"
- Menstrual cramps
- Food poisoning
- Food allergies
- Lactose intolerance
- Pelvic inflammatory disease
- Kidney stones
- Crohn's disease
- Urinary tract infection
- Gastroesophageal reflux disease (GERD)
One of the interesting things about this list is that there are a number of cases where an stomach ache might be a temporary or transitive symptom. In which case the use of essential oils might just be coincidence as the symptom is going to go away regardless meaning that confirmation bias can play role.
Fevers are another tough one to follow-up on as they can fluctuate throughout the day which means that confirmation bias can play a role again if someone sees a fever break following the application of an essential oil. Also, if other forms of fever management are being used in additional to essential oils then the other treatments may play a larger role as well. Lavender commonly gets mentioned as a treatment for fever, but it has the problem of being combined with other common treatments for fever and it's effects, if any, are not easy to isolate.
This is a very interesting as Tea Tree Oil is known to be an effective treatment as an antiviral, antibacterial, and antifungal. It has even been shown to be effective against MRSA. So this is an area were we can give a firm yes to the effectiveness of an essential oil; however, this applies to a specific oil in much the same way that willow bark can be effective for aches and pains: individual oils may be effective, but as a whole you cannot just randomly select one and expect it to be effective.
It is already well know that various scents can have an effect upon a person by siring up memories or having an affect upon your mood. This means that some essential oils may help in some situations just by virtue of changing your mood giving you a more positive outlook. As shown though, some essential oils can have effects; however, in most cases they are unlikely to have an effect or their application might have a greater effect than the oils themselves.