1. Ulex europaeus
2. Ulmus americana
3. Ulmus pumila
4. Ulva compressa
5. Ulva linza
6. Uniola paniculata
7. Urena lobata
8. Urtica dioica
9. Urtica urens
10. Utricularia bifida
11. Utricularia caerulea
12. Utricularia foliosa
13. Utricularia gibba
14. Utricularia minor
15. Utricularia subulata
16. Utricularia vulgaris
17. Uvularia perfoliata
18. Uvularia sessilifolia

uphrasia alpina

• Eyebright  (Euphrasia spp.)

• Usage: Used for eye problems.<wiki/List_of_medicinal_plants#cite_note-theherbbook-7">
• Harmful effects: Side effects may include confusion, headache, tearing, itching, redness, vision problems, sneezing, nausea, toothache, constipation, cough, trouble breathing, trouble sleeping (insomnia), sweating, and others.<wiki/List_of_medicinal_plants#cite_note-94">

Uncaria gambir

• Cat's claw  (Uncaria spp.  (approx. species))

• Claimed to: cure HIV, cancer, viral infections (such as herpes simplex), tremors, fever reduction, high blood pressure, Alzheimer's disease, chronic fatigue syndrome, and almost everything.
• Preparation: The inner bark and/or root of is/are used to make liquid extracts, capsules, and teas. Preparations can also be applied to the skin.
• Popularity: Cat's claw was ranked as the seventh most popular herb in U.S. sales in .<wiki/List_of_medicinal_plants#cite_note-52">
• Research: There is not enough scientific evidence to determine whether cat's claw works for any health condition.<wiki/List_of_medicinal_plants#cite_note-NCCAMCat-53"><wiki/List_of_medicinal_plants#cite_note-ACSCat-54">
• Beneficial effects:

• Small studies in humans have shown a possible benefit of cat's claw in osteoarthritis and rheumatoid arthritis, but no large trials have been done.<wiki/List_of_medicinal_plants#cite_note-NCCAMCat-53"><wiki/List_of_medicinal_plants#cite_note-ACSCat-54">
• In laboratory studies, cat's claw stimulates part of the immune system, but it has not been proven to reduce inflammation or boost the immune system in humans.<wiki/List_of_medicinal_plants#cite_note-NCCAMCat-53"><wiki/List_of_medicinal_plants#cite_note-ACSCat-54">
• The National Institute on Aging funded a study that looked at how cat's claw may affect the brain. Findings may point to new avenues for research in Alzheimer's disease treatment.<wiki/List_of_medicinal_plants#cite_note-NCCAMCat-53"><wiki/List_of_medicinal_plants#cite_note-ACSCat-54">

• Harmful effects:

• It may have an unwanted effect on blood pressure.