  We present predictions for hydrogen and helium emission line luminosities
from circumstellar matter around Type Ia supernovae (SNe Ia) using time
dependent photoionization modeling. ESO/VLT optical echelle spectra of the SN
Ia 2000cx were taken before and up to 70 days after maximum. We detect no
hydrogen and helium lines, and place an upper limit on the mass loss rate for
the putative wind of less than 1.3EE{-5} solar masses per year, assuming a
speed of 10 km/s and solar abundances for the wind. In a helium-enriched case,
the best line to constrain the mass loss would be He I 10,830 A. We confirm the
details of interstellar Na I and Ca II absorption towards SN 2000cx as
discussed by Patat et al., but also find evidence for 6613.56 A Diffuse
Interstellar Band (DIB) absorption in the Milky Way. We discuss measurements of
the X-ray emission from the interaction between the supernova ejecta and the
wind and we re-evaluate observations of SN 1992A obtained 16 days after maximum
by Schlegel & Petre. We find an upper limit of 1.3EE{-5} solar masses per year.
These results, together with the previous observational work on the normal SNe
Ia 1994D and 2001el, disfavour a symbiotic star in the upper mass loss rate
regime from being the likely progenitor scenario for these SNe. To constrain
hydrogen in late time spectra, we present ESO/VLT and ESO/NTT optical and
infrared observations of SNe Ia 1998bu and 2000cx 251-388 days after maximum.
We see no hydrogen line emission in SNe 1998bu and 2000cx at these epochs, and
we argue from modeling that the mass of such hydrogen-rich gas must be less
than 0.03 solar masses for both supernovae. Comparing similar upper limits with
recent models of Pan et al., it seems hydrogen-rich donors with a separation of
less than 5 times the radius of the donor may be ruled out for the five SNe Ia
1998bu, 2000cx, 2001el, 2005am and 2005cf.
